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 $63.25   3.326%   $65.3537   $65.35   $65.35   $65.40  
  Purchase #2 $212.92   6.434%   $226.6193   $226.62   $226.60   $226.60  
  Purchase #3 $99.54   3.160%   $102.6855   $102.69   $102.70   $102.70  
  Purchase #4 $209.47   5.426%   $220.8358   $220.84   $220.85   $220.80  
  Purchase #5 $57.90   13.114%   $65.493   $65.49   $65.50   $65.50  
  Purchase #6 $91.33   11.331%   $101.6786   $101.68   $101.70   $101.70  
  Purchase #7 $89.80   5.173%   $94.4454   $94.45   $94.45   $94.40  
  7 purchase totals = $824.21       $877.1113   $877.12   $877.15   $877.10