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 $192.55   5.867%   $203.8469   $203.85   $203.85   $203.80  
  Purchase #2 $26.27   3.329%   $27.1445   $27.14   $27.15   $27.10  
  Purchase #3 $118.55   5.850%   $125.4852   $125.49   $125.50   $125.50  
  Purchase #4 $158.61   9.726%   $174.0364   $174.04   $174.05   $174.00  
  Purchase #5 $126.76   9.333%   $138.5905   $138.59   $138.60   $138.60  
  Purchase #6 $219.96   10.283%   $242.5785   $242.58   $242.60   $242.60  
  Purchase #7 $227.92   13.125%   $257.8345   $257.83   $257.85   $257.80  
  7 purchase totals = $1,070.62       $1,169.5165   $1,169.52   $1,169.60   $1,169.40