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 $169.43   8.463%   $183.7689   $183.77   $183.75   $183.80  
  Purchase #2 $112.74   8.520%   $122.3454   $122.35   $122.35   $122.30  
  Purchase #3 $204.84   4.462%   $213.98   $213.98   $214.00   $214.00  
  Purchase #4 $60.89   13.560%   $69.1467   $69.15   $69.15   $69.10  
  Purchase #5 $168.28   6.395%   $179.0415   $179.04   $179.05   $179.00  
  Purchase #6 $244.28   9.651%   $267.8555   $267.86   $267.85   $267.90  
  Purchase #7 $153.82   6.711%   $164.1429   $164.14   $164.15   $164.10  
  7 purchase totals = $1,114.28       $1,200.2809   $1,200.29   $1,200.30   $1,200.20