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 $216.46   8.562%   $234.9933   $234.99   $235.00   $235.00  
  Purchase #2 $153.97   7.583%   $165.6455   $165.65   $165.65   $165.60  
  Purchase #3 $116.34   6.698%   $124.1325   $124.13   $124.15   $124.10  
  Purchase #4 $121.93   11.783%   $136.297   $136.30   $136.30   $136.30  
  Purchase #5 $169.78   13.420%   $192.5645   $192.56   $192.55   $192.60  
  Purchase #6 $43.60   5.303%   $45.9121   $45.91   $45.90   $45.90  
  Purchase #7 $159.43   6.222%   $169.3497   $169.35   $169.35   $169.30  
  7 purchase totals = $981.51       $1,068.8946   $1,068.89   $1,068.90   $1,068.80