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 $90.94   5.322%   $95.7798   $95.78   $95.80   $95.80  
  Purchase #2 $241.92   7.644%   $260.4124   $260.41   $260.40   $260.40  
  Purchase #3 $22.29   8.664%   $24.2212   $24.22   $24.20   $24.20  
  Purchase #4 $227.64   10.244%   $250.9594   $250.96   $250.95   $251.00  
  Purchase #5 $8.42   6.121%   $8.9354   $8.94   $8.95   $8.90  
  Purchase #6 $192.53   8.598%   $209.0837   $209.08   $209.10   $209.10  
  Purchase #7 $229.72   10.558%   $253.9738   $253.97   $253.95   $254.00  
  7 purchase totals = $1,013.46       $1,103.3657   $1,103.36   $1,103.35   $1,103.40