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 $94.67   8.430%   $102.6507   $102.65   $102.65   $102.70  
  Purchase #2 $10.58   11.860%   $11.8348   $11.83   $11.85   $11.80  
  Purchase #3 $64.29   8.503%   $69.7566   $69.76   $69.75   $69.80  
  Purchase #4 $187.61   6.263%   $199.36   $199.36   $199.35   $199.40  
  Purchase #5 $134.72   10.292%   $148.5854   $148.59   $148.60   $148.60  
  Purchase #6 $235.42   12.657%   $265.2171   $265.22   $265.20   $265.20  
  Purchase #7 $156.30   7.409%   $167.8803   $167.88   $167.90   $167.90  
  7 purchase totals = $883.59       $965.2849   $965.29   $965.30   $965.40