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 $85.59   7.501%   $92.0101   $92.01   $92.00   $92.00  
  Purchase #2 $231.92   6.214%   $246.3315   $246.33   $246.35   $246.30  
  Purchase #3 $203.61   4.341%   $212.4487   $212.45   $212.45   $212.40  
  Purchase #4 $78.49   11.346%   $87.3955   $87.40   $87.40   $87.40  
  Purchase #5 $236.71   3.793%   $245.6884   $245.69   $245.70   $245.70  
  Purchase #6 $142.70   11.332%   $158.8708   $158.87   $158.85   $158.90  
  Purchase #7 $197.29   6.544%   $210.2007   $210.20   $210.20   $210.20  
  7 purchase totals = $1,176.31       $1,252.9457   $1,252.95   $1,252.95   $1,252.90