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 $69.48   9.667%   $76.1966   $76.20   $76.20   $76.20  
  Purchase #2 $160.84   9.196%   $175.6308   $175.63   $175.65   $175.60  
  Purchase #3 $218.48   3.683%   $226.5266   $226.53   $226.55   $226.50  
  Purchase #4 $46.67   3.304%   $48.212   $48.21   $48.20   $48.20  
  Purchase #5 $68.65   12.530%   $77.2518   $77.25   $77.25   $77.30  
  Purchase #6 $207.46   9.826%   $227.845   $227.85   $227.85   $227.80  
  Purchase #7 $211.68   10.381%   $233.6545   $233.65   $233.65   $233.70  
  7 purchase totals = $983.26       $1,065.3173   $1,065.32   $1,065.35   $1,065.30