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 $62.56   5.625%   $66.079   $66.08   $66.10   $66.10  
  Purchase #2 $155.82   5.425%   $164.2732   $164.27   $164.25   $164.30  
  Purchase #3 $95.57   3.791%   $99.1931   $99.19   $99.20   $99.20  
  Purchase #4 $237.30   12.823%   $267.729   $267.73   $267.75   $267.70  
  Purchase #5 $23.27   8.865%   $25.3329   $25.33   $25.35   $25.30  
  Purchase #6 $204.52   12.644%   $230.3795   $230.38   $230.40   $230.40  
  Purchase #7 $97.99   11.841%   $109.593   $109.59   $109.60   $109.60  
  7 purchase totals = $877.03       $962.5797   $962.57   $962.65   $962.60