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 $89.25   6.404%   $94.9656   $94.97   $94.95   $95.00  
  Purchase #2 $86.31   12.388%   $97.0021   $97.00   $97.00   $97.00  
  Purchase #3 $167.63   9.739%   $183.9555   $183.96   $183.95   $184.00  
  Purchase #4 $228.89   6.423%   $243.5916   $243.59   $243.60   $243.60  
  Purchase #5 $183.91   8.629%   $199.7796   $199.78   $199.80   $199.80  
  Purchase #6 $87.79   11.117%   $97.5496   $97.55   $97.55   $97.50  
  Purchase #7 $239.97   11.485%   $267.5306   $267.53   $267.55   $267.50  
  7 purchase totals = $1,083.75       $1,184.3746   $1,184.38   $1,184.40   $1,184.40