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 $107.29   11.464%   $119.5897   $119.59   $119.60   $119.60  
  Purchase #2 $198.92   7.110%   $213.0632   $213.06   $213.05   $213.10  
  Purchase #3 $96.42   5.644%   $101.8619   $101.86   $101.85   $101.90  
  Purchase #4 $167.94   3.585%   $173.9606   $173.96   $173.95   $174.00  
  Purchase #5 $60.84   4.249%   $63.4251   $63.43   $63.45   $63.40  
  Purchase #6 $118.94   6.771%   $126.9934   $126.99   $127.00   $127.00  
  Purchase #7 $225.80   3.502%   $233.7075   $233.71   $233.70   $233.70  
  7 purchase totals = $976.15       $1,032.6014   $1,032.60   $1,032.60   $1,032.70