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 $214.59   12.612%   $241.6541   $241.65   $241.65   $241.70  
  Purchase #2 $194.57   8.346%   $210.8088   $210.81   $210.80   $210.80  
  Purchase #3 $46.59   8.370%   $50.4896   $50.49   $50.50   $50.50  
  Purchase #4 $38.60   12.495%   $43.4231   $43.42   $43.40   $43.40  
  Purchase #5 $91.95   5.475%   $96.9843   $96.98   $97.00   $97.00  
  Purchase #6 $212.61   4.385%   $221.9329   $221.93   $221.95   $221.90  
  Purchase #7 $156.38   9.133%   $170.6622   $170.66   $170.65   $170.70  
  7 purchase totals = $955.29       $1,035.9550   $1,035.94   $1,035.95   $1,036.00