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 $65.90   4.651%   $68.965   $68.97   $68.95   $69.00  
  Purchase #2 $60.46   9.198%   $66.0211   $66.02   $66.00   $66.00  
  Purchase #3 $164.33   10.727%   $181.9577   $181.96   $181.95   $182.00  
  Purchase #4 $203.52   5.803%   $215.3303   $215.33   $215.35   $215.30  
  Purchase #5 $216.51   3.620%   $224.3477   $224.35   $224.35   $224.30  
  Purchase #6 $119.27   4.598%   $124.754   $124.75   $124.75   $124.80  
  Purchase #7 $175.97   11.296%   $195.8476   $195.85   $195.85   $195.80  
  7 purchase totals = $1,005.96       $1,077.2234   $1,077.23   $1,077.20   $1,077.20