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 $195.58   9.762%   $214.6725   $214.67   $214.65   $214.70  
  Purchase #2 $154.35   9.718%   $169.3497   $169.35   $169.35   $169.30  
  Purchase #3 $31.43   9.116%   $34.2952   $34.30   $34.30   $34.30  
  Purchase #4 $173.46   6.138%   $184.107   $184.11   $184.10   $184.10  
  Purchase #5 $201.75   5.210%   $212.2612   $212.26   $212.25   $212.30  
  Purchase #6 $133.55   12.193%   $149.8338   $149.83   $149.85   $149.80  
  Purchase #7 $233.35   13.712%   $265.347   $265.35   $265.35   $265.30  
  7 purchase totals = $1,123.47       $1,229.8664   $1,229.87   $1,229.85   $1,229.80