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 $194.49   4.738%   $203.7049   $203.70   $203.70   $203.70  
  Purchase #2 $230.96   11.462%   $257.4326   $257.43   $257.45   $257.40  
  Purchase #3 $234.41   4.309%   $244.5107   $244.51   $244.50   $244.50  
  Purchase #4 $159.81   7.464%   $171.7382   $171.74   $171.75   $171.70  
  Purchase #5 $210.52   10.814%   $233.2856   $233.29   $233.30   $233.30  
  Purchase #6 $76.55   8.611%   $83.1417   $83.14   $83.15   $83.10  
  Purchase #7 $250.43   9.460%   $274.1207   $274.12   $274.10   $274.10  
  7 purchase totals = $1,357.17       $1,467.9344   $1,467.93   $1,467.95   $1,467.80