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 $93.48   8.555%   $101.4772   $101.48   $101.50   $101.50  
  Purchase #2 $35.82   5.842%   $37.9126   $37.91   $37.90   $37.90  
  Purchase #3 $216.71   3.247%   $223.7466   $223.75   $223.75   $223.70  
  Purchase #4 $199.52   10.785%   $221.0382   $221.04   $221.05   $221.00  
  Purchase #5 $128.94   12.246%   $144.73   $144.73   $144.75   $144.70  
  Purchase #6 $89.74   9.173%   $97.9719   $97.97   $97.95   $98.00  
  Purchase #7 $246.40   8.861%   $268.2335   $268.23   $268.25   $268.20  
  7 purchase totals = $1,010.61       $1,095.1100   $1,095.11   $1,095.15   $1,095.00