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 $205.96   13.590%   $233.95   $233.95   $233.95   $234.00  
  Purchase #2 $147.55   3.559%   $152.8013   $152.80   $152.80   $152.80  
  Purchase #3 $45.37   7.548%   $48.7945   $48.79   $48.80   $48.80  
  Purchase #4 $225.34   8.404%   $244.2776   $244.28   $244.30   $244.30  
  Purchase #5 $202.86   4.417%   $211.8203   $211.82   $211.80   $211.80  
  Purchase #6 $110.38   5.807%   $116.7898   $116.79   $116.80   $116.80  
  Purchase #7 $22.48   9.584%   $24.6345   $24.63   $24.65   $24.60  
  7 purchase totals = $959.94       $1,033.0680   $1,033.06   $1,033.10   $1,033.10