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 $86.55   10.728%   $95.8351   $95.84   $95.85   $95.80  
  Purchase #2 $201.76   5.460%   $212.7761   $212.78   $212.80   $212.80  
  Purchase #3 $191.28   7.173%   $205.0005   $205.00   $205.00   $205.00  
  Purchase #4 $87.75   7.772%   $94.5699   $94.57   $94.55   $94.60  
  Purchase #5 $8.56   10.670%   $9.4734   $9.47   $9.45   $9.50  
  Purchase #6 $131.70   13.191%   $149.0725   $149.07   $149.05   $149.10  
  Purchase #7 $144.72   9.561%   $158.5567   $158.56   $158.55   $158.60  
  7 purchase totals = $852.32       $925.2842   $925.29   $925.25   $925.40