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 $221.71   7.180%   $237.6288   $237.63   $237.65   $237.60  
  Purchase #2 $147.37   3.644%   $152.7402   $152.74   $152.75   $152.70  
  Purchase #3 $243.37   4.664%   $254.7208   $254.72   $254.70   $254.70  
  Purchase #4 $232.94   5.128%   $244.8852   $244.89   $244.90   $244.90  
  Purchase #5 $168.53   13.813%   $191.809   $191.81   $191.80   $191.80  
  Purchase #6 $164.48   5.806%   $174.0297   $174.03   $174.05   $174.00  
  Purchase #7 $140.95   12.302%   $158.2897   $158.29   $158.30   $158.30  
  7 purchase totals = $1,319.35       $1,414.1034   $1,414.11   $1,414.15   $1,414.00