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 $64.61   8.525%   $70.118   $70.12   $70.10   $70.10  
  Purchase #2 $240.87   7.207%   $258.2295   $258.23   $258.25   $258.20  
  Purchase #3 $154.58   9.726%   $169.6145   $169.61   $169.60   $169.60  
  Purchase #4 $189.87   5.149%   $199.6464   $199.65   $199.65   $199.60  
  Purchase #5 $149.79   4.486%   $156.5096   $156.51   $156.50   $156.50  
  Purchase #6 $25.93   5.471%   $27.3486   $27.35   $27.35   $27.30  
  Purchase #7 $188.98   3.211%   $195.0481   $195.05   $195.05   $195.00  
  7 purchase totals = $1,014.63       $1,076.5147   $1,076.52   $1,076.50   $1,076.30