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 $91.68   4.603%   $95.9   $95.90   $95.90   $95.90  
  Purchase #2 $236.94   13.264%   $268.3677   $268.37   $268.35   $268.40  
  Purchase #3 $196.43   6.799%   $209.7853   $209.79   $209.80   $209.80  
  Purchase #4 $205.61   13.574%   $233.5195   $233.52   $233.50   $233.50  
  Purchase #5 $216.48   6.869%   $231.35   $231.35   $231.35   $231.40  
  Purchase #6 $134.95   4.867%   $141.518   $141.52   $141.50   $141.50  
  Purchase #7 $16.35   5.836%   $17.3042   $17.30   $17.30   $17.30  
  7 purchase totals = $1,098.44       $1,197.7447   $1,197.75   $1,197.70   $1,197.80