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 $61.66   3.227%   $63.6498   $63.65   $63.65   $63.60  
  Purchase #2 $10.68   12.204%   $11.9834   $11.98   $12.00   $12.00  
  Purchase #3 $22.57   13.748%   $25.6729   $25.67   $25.65   $25.70  
  Purchase #4 $106.76   9.248%   $116.6332   $116.63   $116.65   $116.60  
  Purchase #5 $6.93   7.567%   $7.4544   $7.45   $7.45   $7.50  
  Purchase #6 $142.25   11.849%   $159.1052   $159.11   $159.10   $159.10  
  Purchase #7 $10.28   6.570%   $10.9554   $10.96   $10.95   $11.00  
  7 purchase totals = $361.13       $395.4543   $395.45   $395.45   $395.50