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 $174.80   13.250%   $197.961   $197.96   $197.95   $198.00  
  Purchase #2 $10.35   11.254%   $11.5148   $11.51   $11.50   $11.50  
  Purchase #3 $65.52   7.793%   $70.626   $70.63   $70.65   $70.60  
  Purchase #4 $156.46   8.273%   $169.4039   $169.40   $169.40   $169.40  
  Purchase #5 $188.54   10.144%   $207.6655   $207.67   $207.65   $207.70  
  Purchase #6 $36.79   11.268%   $40.9355   $40.94   $40.95   $40.90  
  Purchase #7 $192.41   3.560%   $199.2598   $199.26   $199.25   $199.30  
  7 purchase totals = $824.87       $897.3665   $897.37   $897.35   $897.40