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 $210.99   5.313%   $222.1999   $222.20   $222.20   $222.20  
  Purchase #2 $68.79   7.121%   $73.6885   $73.69   $73.70   $73.70  
  Purchase #3 $14.36   11.773%   $16.0506   $16.05   $16.05   $16.10  
  Purchase #4 $221.31   4.222%   $230.6537   $230.65   $230.65   $230.70  
  Purchase #5 $99.82   8.707%   $108.5113   $108.51   $108.50   $108.50  
  Purchase #6 $65.71   8.503%   $71.2973   $71.30   $71.30   $71.30  
  Purchase #7 $31.84   5.221%   $33.5024   $33.50   $33.50   $33.50  
  7 purchase totals = $712.82       $755.9037   $755.90   $755.90   $756.00