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 $174.76   12.164%   $196.0178   $196.02   $196.00   $196.00  
  Purchase #2 $101.75   7.282%   $109.1594   $109.16   $109.15   $109.20  
  Purchase #3 $168.74   4.665%   $176.6117   $176.61   $176.60   $176.60  
  Purchase #4 $245.99   10.591%   $272.0428   $272.04   $272.05   $272.00  
  Purchase #5 $138.82   7.811%   $149.6632   $149.66   $149.65   $149.70  
  Purchase #6 $169.91   10.210%   $187.2578   $187.26   $187.25   $187.30  
  Purchase #7 $20.26   4.757%   $21.2238   $21.22   $21.20   $21.20  
  7 purchase totals = $1,020.23       $1,111.9765   $1,111.97   $1,111.90   $1,112.00