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 $62.91   3.263%   $64.9628   $64.96   $64.95   $65.00  
  Purchase #2 $190.77   10.577%   $210.9477   $210.95   $210.95   $210.90  
  Purchase #3 $114.77   3.191%   $118.4323   $118.43   $118.45   $118.40  
  Purchase #4 $178.30   6.199%   $189.3528   $189.35   $189.35   $189.40  
  Purchase #5 $188.74   12.327%   $212.006   $212.01   $212.00   $212.00  
  Purchase #6 $245.85   4.286%   $256.3871   $256.39   $256.40   $256.40  
  Purchase #7 $159.56   10.736%   $176.6904   $176.69   $176.70   $176.70  
  7 purchase totals = $1,140.90       $1,228.7791   $1,228.78   $1,228.80   $1,228.80