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 $232.83   8.462%   $252.5321   $252.53   $252.55   $252.50  
  Purchase #2 $213.51   3.658%   $221.3202   $221.32   $221.30   $221.30  
  Purchase #3 $186.30   13.112%   $210.7277   $210.73   $210.75   $210.70  
  Purchase #4 $158.55   6.867%   $169.4376   $169.44   $169.45   $169.40  
  Purchase #5 $61.38   3.463%   $63.5056   $63.51   $63.50   $63.50  
  Purchase #6 $122.92   7.861%   $132.5827   $132.58   $132.60   $132.60  
  Purchase #7 $168.52   8.144%   $182.2443   $182.24   $182.25   $182.20  
  7 purchase totals = $1,144.01       $1,232.3502   $1,232.35   $1,232.40   $1,232.20