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 $41.76   7.251%   $44.788   $44.79   $44.80   $44.80  
  Purchase #2 $162.87   13.447%   $184.7711   $184.77   $184.75   $184.80  
  Purchase #3 $115.30   4.353%   $120.319   $120.32   $120.30   $120.30  
  Purchase #4 $94.32   9.578%   $103.354   $103.35   $103.35   $103.40  
  Purchase #5 $212.31   7.332%   $227.8766   $227.88   $227.90   $227.90  
  Purchase #6 $244.96   5.582%   $258.6337   $258.63   $258.65   $258.60  
  Purchase #7 $84.52   12.126%   $94.7689   $94.77   $94.75   $94.80  
  7 purchase totals = $956.04       $1,034.5113   $1,034.51   $1,034.50   $1,034.60