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 $44.46   4.561%   $46.4878   $46.49   $46.50   $46.50  
  Purchase #2 $69.89   3.121%   $72.0713   $72.07   $72.05   $72.10  
  Purchase #3 $242.36   11.548%   $270.3477   $270.35   $270.35   $270.30  
  Purchase #4 $66.61   12.282%   $74.791   $74.79   $74.80   $74.80  
  Purchase #5 $186.76   6.740%   $199.3476   $199.35   $199.35   $199.30  
  Purchase #6 $150.33   11.496%   $167.6119   $167.61   $167.60   $167.60  
  Purchase #7 $204.43   3.323%   $211.2232   $211.22   $211.20   $211.20  
  7 purchase totals = $964.84       $1,041.8805   $1,041.88   $1,041.85   $1,041.80