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 $174.39   11.459%   $194.3734   $194.37   $194.35   $194.40  
  Purchase #2 $75.58   12.514%   $85.0381   $85.04   $85.05   $85.00  
  Purchase #3 $11.48   9.821%   $12.6075   $12.61   $12.60   $12.60  
  Purchase #4 $22.42   9.381%   $24.5232   $24.52   $24.50   $24.50  
  Purchase #5 $189.97   8.722%   $206.5392   $206.54   $206.55   $206.50  
  Purchase #6 $244.34   3.199%   $252.1564   $252.16   $252.15   $252.20  
  Purchase #7 $248.89   11.461%   $277.4153   $277.42   $277.40   $277.40  
  7 purchase totals = $967.07       $1,052.6531   $1,052.66   $1,052.60   $1,052.60