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 $69.37   7.723%   $74.7274   $74.73   $74.75   $74.70  
  Purchase #2 $59.41   4.281%   $61.9533   $61.95   $61.95   $62.00  
  Purchase #3 $91.37   9.774%   $100.3005   $100.30   $100.30   $100.30  
  Purchase #4 $160.52   3.534%   $166.1928   $166.19   $166.20   $166.20  
  Purchase #5 $244.82   3.398%   $253.139   $253.14   $253.15   $253.10  
  Purchase #6 $245.63   8.377%   $266.2064   $266.21   $266.20   $266.20  
  Purchase #7 $128.32   8.662%   $139.4351   $139.44   $139.45   $139.40  
  7 purchase totals = $999.44       $1,061.9545   $1,061.96   $1,062.00   $1,061.90