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 $31.27   8.514%   $33.9323   $33.93   $33.95   $33.90  
  Purchase #2 $221.81   10.658%   $245.4505   $245.45   $245.45   $245.50  
  Purchase #3 $94.93   11.789%   $106.1213   $106.12   $106.10   $106.10  
  Purchase #4 $57.62   4.659%   $60.3045   $60.30   $60.30   $60.30  
  Purchase #5 $222.90   9.218%   $243.4469   $243.45   $243.45   $243.40  
  Purchase #6 $234.92   3.355%   $242.8016   $242.80   $242.80   $242.80  
  Purchase #7 $114.93   11.552%   $128.2067   $128.21   $128.20   $128.20  
  7 purchase totals = $978.38       $1,060.2638   $1,060.26   $1,060.25   $1,060.20