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 $54.54   11.385%   $60.7494   $60.75   $60.75   $60.70  
  Purchase #2 $211.38   12.157%   $237.0775   $237.08   $237.10   $237.10  
  Purchase #3 $172.95   5.223%   $181.9832   $181.98   $182.00   $182.00  
  Purchase #4 $241.70   7.215%   $259.1387   $259.14   $259.15   $259.10  
  Purchase #5 $237.27   3.145%   $244.7321   $244.73   $244.75   $244.70  
  Purchase #6 $87.89   10.577%   $97.1861   $97.19   $97.20   $97.20  
  Purchase #7 $246.54   7.241%   $264.392   $264.39   $264.40   $264.40  
  7 purchase totals = $1,252.27       $1,345.2590   $1,345.26   $1,345.35   $1,345.20