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 $173.92   12.668%   $195.9522   $195.95   $195.95   $196.00  
  Purchase #2 $6.42   13.577%   $7.2916   $7.29   $7.30   $7.30  
  Purchase #3 $238.52   8.664%   $259.1854   $259.19   $259.20   $259.20  
  Purchase #4 $55.39   4.472%   $57.867   $57.87   $57.85   $57.90  
  Purchase #5 $145.94   4.725%   $152.8357   $152.84   $152.85   $152.80  
  Purchase #6 $174.90   4.598%   $182.9419   $182.94   $182.95   $182.90  
  Purchase #7 $149.53   11.864%   $167.2702   $167.27   $167.25   $167.30  
  7 purchase totals = $944.62       $1,023.3440   $1,023.35   $1,023.35   $1,023.40