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 $173.97   12.605%   $195.8989   $195.90   $195.90   $195.90  
  Purchase #2 $149.56   3.734%   $155.1446   $155.14   $155.15   $155.10  
  Purchase #3 $148.41   12.642%   $167.172   $167.17   $167.15   $167.20  
  Purchase #4 $140.30   13.832%   $159.7063   $159.71   $159.70   $159.70  
  Purchase #5 $86.52   11.727%   $96.6662   $96.67   $96.65   $96.70  
  Purchase #6 $201.73   4.415%   $210.6364   $210.64   $210.65   $210.60  
  Purchase #7 $43.49   13.636%   $49.4203   $49.42   $49.40   $49.40  
  7 purchase totals = $943.98       $1,034.6447   $1,034.65   $1,034.60   $1,034.60