Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
  Case Tag  
Price  
Sales  
Tax %  
Raw Total  
Incl. Sales Tax  
Rounded  
to Penny  
Rounded  
to Nickel  
Rounded  
to Dime  
  Purchase #1 $117.82   5.263%   $124.0209   $124.02   $124.00   $124.00  
  Purchase #2 $247.80   5.845%   $262.2839   $262.28   $262.30   $262.30  
  Purchase #3 $169.87   10.856%   $188.3111   $188.31   $188.30   $188.30  
  Purchase #4 $169.61   4.667%   $177.5257   $177.53   $177.55   $177.50  
  Purchase #5 $115.88   8.751%   $126.0207   $126.02   $126.00   $126.00  
  Purchase #6 $154.86   9.824%   $170.0734   $170.07   $170.05   $170.10  
  Purchase #7 $201.38   9.634%   $220.7809   $220.78   $220.80   $220.80  
  7 purchase totals = $1,177.22       $1,269.0166   $1,269.01   $1,269.00   $1,269.00