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 $87.86   8.173%   $95.0408   $95.04   $95.05   $95.00  
  Purchase #2 $161.52   7.474%   $173.592   $173.59   $173.60   $173.60  
  Purchase #3 $184.55   11.482%   $205.74   $205.74   $205.75   $205.70  
  Purchase #4 $46.31   5.345%   $48.7853   $48.79   $48.80   $48.80  
  Purchase #5 $61.92   4.568%   $64.7485   $64.75   $64.75   $64.70  
  Purchase #6 $23.25   11.313%   $25.8803   $25.88   $25.90   $25.90  
  Purchase #7 $181.82   13.340%   $206.0748   $206.07   $206.05   $206.10  
  7 purchase totals = $747.23       $819.8617   $819.86   $819.90   $819.80