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 $45.55   3.729%   $47.2486   $47.25   $47.25   $47.20  
  Purchase #2 $223.58   12.603%   $251.7578   $251.76   $251.75   $251.80  
  Purchase #3 $233.56   9.567%   $255.9047   $255.90   $255.90   $255.90  
  Purchase #4 $56.86   4.310%   $59.3107   $59.31   $59.30   $59.30  
  Purchase #5 $160.42   8.278%   $173.6996   $173.70   $173.70   $173.70  
  Purchase #6 $235.59   3.851%   $244.6626   $244.66   $244.65   $244.70  
  Purchase #7 $214.41   6.703%   $228.7819   $228.78   $228.80   $228.80  
  7 purchase totals = $1,169.97       $1,261.3659   $1,261.36   $1,261.35   $1,261.40