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 $119.27   4.479%   $124.6121   $124.61   $124.60   $124.60  
  Purchase #2 $198.43   6.522%   $211.3716   $211.37   $211.35   $211.40  
  Purchase #3 $234.53   5.342%   $247.0586   $247.06   $247.05   $247.10  
  Purchase #4 $236.79   3.364%   $244.7556   $244.76   $244.75   $244.80  
  Purchase #5 $134.49   8.546%   $145.9835   $145.98   $146.00   $146.00  
  Purchase #6 $119.39   8.160%   $129.1322   $129.13   $129.15   $129.10  
  Purchase #7 $218.52   6.575%   $232.8877   $232.89   $232.90   $232.90  
  7 purchase totals = $1,261.42       $1,335.8013   $1,335.80   $1,335.80   $1,335.90