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 $184.48   11.128%   $205.0089   $205.01   $205.00   $205.00  
  Purchase #2 $193.31   12.492%   $217.4583   $217.46   $217.45   $217.50  
  Purchase #3 $153.50   9.445%   $167.9981   $168.00   $168.00   $168.00  
  Purchase #4 $98.96   3.808%   $102.7284   $102.73   $102.75   $102.70  
  Purchase #5 $95.56   13.439%   $108.4023   $108.40   $108.40   $108.40  
  Purchase #6 $86.66   9.502%   $94.8944   $94.89   $94.90   $94.90  
  Purchase #7 $202.44   5.113%   $212.7908   $212.79   $212.80   $212.80  
  7 purchase totals = $1,014.91       $1,109.2812   $1,109.28   $1,109.30   $1,109.30