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 $43.90   6.505%   $46.7557   $46.76   $46.75   $46.80  
  Purchase #2 $164.93   11.355%   $183.6578   $183.66   $183.65   $183.70  
  Purchase #3 $77.95   5.301%   $82.0821   $82.08   $82.10   $82.10  
  Purchase #4 $143.70   6.821%   $153.5018   $153.50   $153.50   $153.50  
  Purchase #5 $172.87   12.413%   $194.3284   $194.33   $194.35   $194.30  
  Purchase #6 $170.83   3.846%   $177.4001   $177.40   $177.40   $177.40  
  Purchase #7 $97.48   7.525%   $104.8154   $104.82   $104.80   $104.80  
  7 purchase totals = $871.66       $942.5413   $942.55   $942.55   $942.60