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 $95.78   10.611%   $105.9432   $105.94   $105.95   $105.90  
  Purchase #2 $181.37   10.416%   $200.2615   $200.26   $200.25   $200.30  
  Purchase #3 $85.92   10.188%   $94.6735   $94.67   $94.65   $94.70  
  Purchase #4 $109.65   6.137%   $116.3792   $116.38   $116.40   $116.40  
  Purchase #5 $195.37   11.552%   $217.9391   $217.94   $217.95   $217.90  
  Purchase #6 $239.30   12.558%   $269.3513   $269.35   $269.35   $269.40  
  Purchase #7 $184.72   13.615%   $209.8696   $209.87   $209.85   $209.90  
  7 purchase totals = $1,092.11       $1,214.4174   $1,214.41   $1,214.40   $1,214.50