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   3.363%   $63.7336   $63.73   $63.75   $63.70  
  Purchase #2 $72.57   13.273%   $82.2022   $82.20   $82.20   $82.20  
  Purchase #3 $194.40   12.521%   $218.7408   $218.74   $218.75   $218.70  
  Purchase #4 $172.43   5.559%   $182.0154   $182.02   $182.00   $182.00  
  Purchase #5 $151.67   5.713%   $160.3349   $160.33   $160.35   $160.30  
  Purchase #6 $196.90   13.294%   $223.0759   $223.08   $223.10   $223.10  
  Purchase #7 $5.58   7.383%   $5.992   $5.99   $6.00   $6.00  
  7 purchase totals = $855.21       $936.0948   $936.09   $936.15   $936.00