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 $44.76   4.180%   $46.631   $46.63   $46.65   $46.60  
  Purchase #2 $230.62   8.691%   $250.6632   $250.66   $250.65   $250.70  
  Purchase #3 $32.72   5.707%   $34.5873   $34.59   $34.60   $34.60  
  Purchase #4 $125.43   5.326%   $132.1104   $132.11   $132.10   $132.10  
  Purchase #5 $226.48   6.125%   $240.3519   $240.35   $240.35   $240.40  
  Purchase #6 $99.55   10.535%   $110.0376   $110.04   $110.05   $110.00  
  Purchase #7 $197.82   12.809%   $223.1588   $223.16   $223.15   $223.20  
  7 purchase totals = $957.38       $1,037.5402   $1,037.54   $1,037.55   $1,037.60