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 $69.27   8.261%   $74.9924   $74.99   $75.00   $75.00  
  Purchase #2 $133.30   9.700%   $146.2301   $146.23   $146.25   $146.20  
  Purchase #3 $210.72   7.559%   $226.6483   $226.65   $226.65   $226.60  
  Purchase #4 $245.50   4.133%   $255.6465   $255.65   $255.65   $255.60  
  Purchase #5 $138.66   6.676%   $147.9169   $147.92   $147.90   $147.90  
  Purchase #6 $245.53   4.455%   $256.4684   $256.47   $256.45   $256.50  
  Purchase #7 $57.86   4.268%   $60.3295   $60.33   $60.35   $60.30  
  7 purchase totals = $1,100.84       $1,168.2321   $1,168.24   $1,168.25   $1,168.10