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 $186.27   4.672%   $194.9725   $194.97   $194.95   $195.00  
  Purchase #2 $160.53   7.674%   $172.8491   $172.85   $172.85   $172.80  
  Purchase #3 $96.77   5.480%   $102.073   $102.07   $102.05   $102.10  
  Purchase #4 $21.89   11.590%   $24.4271   $24.43   $24.45   $24.40  
  Purchase #5 $129.59   9.734%   $142.2043   $142.20   $142.20   $142.20  
  Purchase #6 $207.74   8.311%   $225.0053   $225.01   $225.00   $225.00  
  Purchase #7 $172.81   9.438%   $189.1198   $189.12   $189.10   $189.10  
  7 purchase totals = $975.60       $1,050.6511   $1,050.65   $1,050.60   $1,050.60