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 $88.70   8.753%   $96.4639   $96.46   $96.45   $96.50  
  Purchase #2 $96.89   10.656%   $107.2146   $107.21   $107.20   $107.20  
  Purchase #3 $248.36   9.660%   $272.3516   $272.35   $272.35   $272.40  
  Purchase #4 $212.88   10.530%   $235.2963   $235.30   $235.30   $235.30  
  Purchase #5 $238.94   6.381%   $254.1868   $254.19   $254.20   $254.20  
  Purchase #6 $141.94   12.664%   $159.9153   $159.92   $159.90   $159.90  
  Purchase #7 $73.98   11.279%   $82.3242   $82.32   $82.30   $82.30  
  7 purchase totals = $1,101.69       $1,207.7527   $1,207.75   $1,207.70   $1,207.80