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 $219.69   11.154%   $244.1942   $244.19   $244.20   $244.20  
  Purchase #2 $238.79   5.347%   $251.5581   $251.56   $251.55   $251.60  
  Purchase #3 $102.59   12.468%   $115.3809   $115.38   $115.40   $115.40  
  Purchase #4 $163.87   11.437%   $182.6118   $182.61   $182.60   $182.60  
  Purchase #5 $221.64   13.868%   $252.377   $252.38   $252.40   $252.40  
  Purchase #6 $13.89   4.501%   $14.5152   $14.52   $14.50   $14.50  
  Purchase #7 $227.98   6.199%   $242.1125   $242.11   $242.10   $242.10  
  7 purchase totals = $1,188.45       $1,302.7497   $1,302.75   $1,302.75   $1,302.80