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 $92.63   9.570%   $101.4947   $101.49   $101.50   $101.50  
  Purchase #2 $229.55   9.619%   $251.6304   $251.63   $251.65   $251.60  
  Purchase #3 $24.26   11.694%   $27.097   $27.10   $27.10   $27.10  
  Purchase #4 $226.52   7.601%   $243.7378   $243.74   $243.75   $243.70  
  Purchase #5 $216.79   4.791%   $227.1764   $227.18   $227.20   $227.20  
  Purchase #6 $126.96   8.157%   $137.3161   $137.32   $137.30   $137.30  
  Purchase #7 $210.29   3.109%   $216.8279   $216.83   $216.85   $216.80  
  7 purchase totals = $1,127.00       $1,205.2803   $1,205.29   $1,205.35   $1,205.20