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 $201.26   6.506%   $214.354   $214.35   $214.35   $214.40  
  Purchase #2 $56.51   3.480%   $58.4765   $58.48   $58.50   $58.50  
  Purchase #3 $196.68   4.369%   $205.2729   $205.27   $205.25   $205.30  
  Purchase #4 $118.45   6.218%   $125.8152   $125.82   $125.80   $125.80  
  Purchase #5 $23.97   4.340%   $25.0103   $25.01   $25.00   $25.00  
  Purchase #6 $56.79   4.211%   $59.1814   $59.18   $59.20   $59.20  
  Purchase #7 $88.74   5.610%   $93.7183   $93.72   $93.70   $93.70  
  7 purchase totals = $742.40       $781.8286   $781.83   $781.80   $781.90