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 $193.61   9.802%   $212.5877   $212.59   $212.60   $212.60  
  Purchase #2 $179.98   8.121%   $194.5962   $194.60   $194.60   $194.60  
  Purchase #3 $213.30   4.669%   $223.259   $223.26   $223.25   $223.30  
  Purchase #4 $58.95   4.752%   $61.7513   $61.75   $61.75   $61.80  
  Purchase #5 $156.52   5.505%   $165.1364   $165.14   $165.15   $165.10  
  Purchase #6 $239.93   12.492%   $269.9021   $269.90   $269.90   $269.90  
  Purchase #7 $27.30   6.608%   $29.104   $29.10   $29.10   $29.10  
  7 purchase totals = $1,069.59       $1,156.3367   $1,156.34   $1,156.35   $1,156.40