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 $219.32   7.267%   $235.258   $235.26   $235.25   $235.30  
  Purchase #2 $148.68   11.633%   $165.9759   $165.98   $166.00   $166.00  
  Purchase #3 $159.26   4.468%   $166.3757   $166.38   $166.40   $166.40  
  Purchase #4 $248.97   8.397%   $269.876   $269.88   $269.90   $269.90  
  Purchase #5 $87.97   6.737%   $93.8965   $93.90   $93.90   $93.90  
  Purchase #6 $20.91   5.702%   $22.1023   $22.10   $22.10   $22.10  
  Purchase #7 $181.60   7.390%   $195.0202   $195.02   $195.00   $195.00  
  7 purchase totals = $1,066.71       $1,148.5046   $1,148.52   $1,148.55   $1,148.60