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 $207.41   13.452%   $235.3108   $235.31   $235.30   $235.30  
  Purchase #2 $198.76   3.253%   $205.2257   $205.23   $205.25   $205.20  
  Purchase #3 $135.68   9.610%   $148.7188   $148.72   $148.70   $148.70  
  Purchase #4 $167.95   11.267%   $186.8729   $186.87   $186.85   $186.90  
  Purchase #5 $86.75   9.565%   $95.0476   $95.05   $95.05   $95.00  
  Purchase #6 $94.75   4.697%   $99.2004   $99.20   $99.20   $99.20  
  Purchase #7 $129.68   6.677%   $138.3387   $138.34   $138.35   $138.30  
  7 purchase totals = $1,020.98       $1,108.7149   $1,108.72   $1,108.70   $1,108.60