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 $214.90   9.282%   $234.847   $234.85   $234.85   $234.80  
  Purchase #2 $65.57   4.280%   $68.3764   $68.38   $68.40   $68.40  
  Purchase #3 $157.28   6.533%   $167.5551   $167.56   $167.55   $167.60  
  Purchase #4 $234.39   5.837%   $248.0713   $248.07   $248.05   $248.10  
  Purchase #5 $233.96   3.692%   $242.5978   $242.60   $242.60   $242.60  
  Purchase #6 $200.98   8.113%   $217.2855   $217.29   $217.30   $217.30  
  Purchase #7 $41.83   12.547%   $47.0784   $47.08   $47.10   $47.10  
  7 purchase totals = $1,148.91       $1,225.8115   $1,225.83   $1,225.85   $1,225.90