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 $116.25   6.252%   $123.518   $123.52   $123.50   $123.50  
  Purchase #2 $224.27   8.694%   $243.768   $243.77   $243.75   $243.80  
  Purchase #3 $25.58   11.248%   $28.4572   $28.46   $28.45   $28.50  
  Purchase #4 $173.82   8.703%   $188.9476   $188.95   $188.95   $188.90  
  Purchase #5 $201.88   4.413%   $210.789   $210.79   $210.80   $210.80  
  Purchase #6 $250.33   13.531%   $284.2022   $284.20   $284.20   $284.20  
  Purchase #7 $65.73   11.580%   $73.3415   $73.34   $73.35   $73.30  
  7 purchase totals = $1,057.86       $1,153.0235   $1,153.03   $1,153.00   $1,153.00