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 $91.95   6.782%   $98.186   $98.19   $98.20   $98.20  
  Purchase #2 $115.30   10.374%   $127.2612   $127.26   $127.25   $127.30  
  Purchase #3 $205.35   3.150%   $211.8185   $211.82   $211.80   $211.80  
  Purchase #4 $66.75   3.391%   $69.0135   $69.01   $69.00   $69.00  
  Purchase #5 $203.85   11.678%   $227.6556   $227.66   $227.65   $227.70  
  Purchase #6 $42.32   4.451%   $44.2037   $44.20   $44.20   $44.20  
  Purchase #7 $197.36   9.631%   $216.3677   $216.37   $216.35   $216.40  
  7 purchase totals = $922.88       $994.5062   $994.51   $994.45   $994.60