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 $53.81   5.835%   $56.9498   $56.95   $56.95   $56.90  
  Purchase #2 $195.50   7.555%   $210.27   $210.27   $210.25   $210.30  
  Purchase #3 $187.75   7.161%   $201.1948   $201.19   $201.20   $201.20  
  Purchase #4 $245.92   8.747%   $267.4306   $267.43   $267.45   $267.40  
  Purchase #5 $236.83   4.360%   $247.1558   $247.16   $247.15   $247.20  
  Purchase #6 $223.82   3.745%   $232.2021   $232.20   $232.20   $232.20  
  Purchase #7 $152.82   9.363%   $167.1285   $167.13   $167.15   $167.10  
  7 purchase totals = $1,296.45       $1,382.3316   $1,382.33   $1,382.35   $1,382.30