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 $161.86   7.793%   $174.4737   $174.47   $174.45   $174.50  
  Purchase #2 $26.27   3.530%   $27.1973   $27.20   $27.20   $27.20  
  Purchase #3 $148.50   3.633%   $153.895   $153.90   $153.90   $153.90  
  Purchase #4 $100.29   4.108%   $104.4099   $104.41   $104.40   $104.40  
  Purchase #5 $128.30   11.600%   $143.1828   $143.18   $143.20   $143.20  
  Purchase #6 $84.73   13.245%   $95.9525   $95.95   $95.95   $96.00  
  Purchase #7 $79.31   10.752%   $87.8374   $87.84   $87.85   $87.80  
  7 purchase totals = $729.26       $786.9486   $786.95   $786.95   $787.00