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 $153.66   13.826%   $174.905   $174.91   $174.90   $174.90  
  Purchase #2 $59.40   4.330%   $61.972   $61.97   $61.95   $62.00  
  Purchase #3 $96.29   10.212%   $106.1231   $106.12   $106.10   $106.10  
  Purchase #4 $202.72   6.424%   $215.7427   $215.74   $215.75   $215.70  
  Purchase #5 $183.37   9.616%   $201.0029   $201.00   $201.00   $201.00  
  Purchase #6 $201.63   5.704%   $213.131   $213.13   $213.15   $213.10  
  Purchase #7 $189.58   3.374%   $195.9764   $195.98   $196.00   $196.00  
  7 purchase totals = $1,086.65       $1,168.8531   $1,168.85   $1,168.85   $1,168.80