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 $87.82   7.157%   $94.1053   $94.11   $94.10   $94.10  
  Purchase #2 $243.58   10.352%   $268.7954   $268.80   $268.80   $268.80  
  Purchase #3 $67.75   8.526%   $73.5264   $73.53   $73.55   $73.50  
  Purchase #4 $132.65   8.112%   $143.4106   $143.41   $143.40   $143.40  
  Purchase #5 $178.81   12.425%   $201.0271   $201.03   $201.05   $201.00  
  Purchase #6 $10.64   7.751%   $11.4647   $11.46   $11.45   $11.50  
  Purchase #7 $75.69   5.281%   $79.6872   $79.69   $79.70   $79.70  
  7 purchase totals = $796.94       $872.0167   $872.03   $872.05   $872.00