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 $168.48   8.641%   $183.0384   $183.04   $183.05   $183.00  
  Purchase #2 $212.84   6.855%   $227.4302   $227.43   $227.45   $227.40  
  Purchase #3 $229.69   10.735%   $254.3472   $254.35   $254.35   $254.30  
  Purchase #4 $109.87   8.417%   $119.1178   $119.12   $119.10   $119.10  
  Purchase #5 $161.54   7.170%   $173.1224   $173.12   $173.10   $173.10  
  Purchase #6 $186.95   5.188%   $196.649   $196.65   $196.65   $196.60  
  Purchase #7 $58.78   4.333%   $61.3269   $61.33   $61.35   $61.30  
  7 purchase totals = $1,128.15       $1,215.0319   $1,215.04   $1,215.05   $1,214.80