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 $175.99   10.489%   $194.4496   $194.45   $194.45   $194.40  
  Purchase #2 $206.91   9.850%   $227.2906   $227.29   $227.30   $227.30  
  Purchase #3 $60.57   13.174%   $68.5495   $68.55   $68.55   $68.50  
  Purchase #4 $179.74   4.350%   $187.5587   $187.56   $187.55   $187.60  
  Purchase #5 $50.26   7.585%   $54.0722   $54.07   $54.05   $54.10  
  Purchase #6 $31.83   10.355%   $35.126   $35.13   $35.15   $35.10  
  Purchase #7 $121.67   5.857%   $128.7962   $128.80   $128.80   $128.80  
  7 purchase totals = $826.97       $895.8428   $895.85   $895.85   $895.80