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 $90.67   5.816%   $95.9434   $95.94   $95.95   $95.90  
  Purchase #2 $231.49   6.731%   $247.0716   $247.07   $247.05   $247.10  
  Purchase #3 $94.27   10.142%   $103.8309   $103.83   $103.85   $103.80  
  Purchase #4 $247.88   7.141%   $265.5811   $265.58   $265.60   $265.60  
  Purchase #5 $32.30   5.839%   $34.186   $34.19   $34.20   $34.20  
  Purchase #6 $164.88   6.207%   $175.1141   $175.11   $175.10   $175.10  
  Purchase #7 $67.31   9.352%   $73.6048   $73.60   $73.60   $73.60  
  7 purchase totals = $928.80       $995.3319   $995.32   $995.35   $995.30