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 $151.69   11.419%   $169.0115   $169.01   $169.00   $169.00  
  Purchase #2 $84.97   8.386%   $92.0956   $92.10   $92.10   $92.10  
  Purchase #3 $151.33   7.453%   $162.6086   $162.61   $162.60   $162.60  
  Purchase #4 $194.63   5.110%   $204.5756   $204.58   $204.60   $204.60  
  Purchase #5 $38.93   13.701%   $44.2638   $44.26   $44.25   $44.30  
  Purchase #6 $171.96   13.753%   $195.6097   $195.61   $195.60   $195.60  
  Purchase #7 $170.59   6.849%   $182.2737   $182.27   $182.25   $182.30  
  7 purchase totals = $964.10       $1,050.4385   $1,050.44   $1,050.40   $1,050.50