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 $219.43   7.547%   $235.9904   $235.99   $236.00   $236.00  
  Purchase #2 $203.98   4.337%   $212.8266   $212.83   $212.85   $212.80  
  Purchase #3 $211.33   7.757%   $227.7229   $227.72   $227.70   $227.70  
  Purchase #4 $76.38   13.588%   $86.7585   $86.76   $86.75   $86.80  
  Purchase #5 $186.49   7.737%   $200.9187   $200.92   $200.90   $200.90  
  Purchase #6 $216.94   8.194%   $234.7161   $234.72   $234.70   $234.70  
  Purchase #7 $194.32   6.309%   $206.5796   $206.58   $206.60   $206.60  
  7 purchase totals = $1,308.87       $1,405.5128   $1,405.52   $1,405.50   $1,405.50