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 $226.43   8.636%   $245.9845   $245.98   $246.00   $246.00  
  Purchase #2 $94.27   8.115%   $101.92   $101.92   $101.90   $101.90  
  Purchase #3 $105.80   12.414%   $118.934   $118.93   $118.95   $118.90  
  Purchase #4 $197.60   11.204%   $219.7391   $219.74   $219.75   $219.70  
  Purchase #5 $222.69   13.621%   $253.0226   $253.02   $253.00   $253.00  
  Purchase #6 $47.81   8.812%   $52.023   $52.02   $52.00   $52.00  
  Purchase #7 $199.76   8.431%   $216.6018   $216.60   $216.60   $216.60  
  7 purchase totals = $1,094.36       $1,208.2250   $1,208.21   $1,208.20   $1,208.10