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 $232.93   5.460%   $245.648   $245.65   $245.65   $245.60  
  Purchase #2 $179.91   13.739%   $204.6278   $204.63   $204.65   $204.60  
  Purchase #3 $95.95   4.527%   $100.2937   $100.29   $100.30   $100.30  
  Purchase #4 $210.29   8.540%   $228.2488   $228.25   $228.25   $228.20  
  Purchase #5 $22.54   3.844%   $23.4064   $23.41   $23.40   $23.40  
  Purchase #6 $56.37   12.708%   $63.5335   $63.53   $63.55   $63.50  
  Purchase #7 $150.91   13.377%   $171.0972   $171.10   $171.10   $171.10  
  7 purchase totals = $948.90       $1,036.8554   $1,036.86   $1,036.90   $1,036.70