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 $84.29   13.312%   $95.5107   $95.51   $95.50   $95.50  
  Purchase #2 $132.86   10.520%   $146.8369   $146.84   $146.85   $146.80  
  Purchase #3 $196.48   4.696%   $205.7067   $205.71   $205.70   $205.70  
  Purchase #4 $124.26   11.534%   $138.5921   $138.59   $138.60   $138.60  
  Purchase #5 $206.43   3.107%   $212.8438   $212.84   $212.85   $212.80  
  Purchase #6 $23.89   9.504%   $26.1605   $26.16   $26.15   $26.20  
  Purchase #7 $184.97   11.567%   $206.3655   $206.37   $206.35   $206.40  
  7 purchase totals = $953.18       $1,032.0162   $1,032.02   $1,032.00   $1,032.00