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 $60.96   11.558%   $68.0058   $68.01   $68.00   $68.00  
  Purchase #2 $230.47   10.782%   $255.3193   $255.32   $255.30   $255.30  
  Purchase #3 $210.40   8.546%   $228.3808   $228.38   $228.40   $228.40  
  Purchase #4 $236.70   12.689%   $266.7349   $266.73   $266.75   $266.70  
  Purchase #5 $40.58   13.683%   $46.1326   $46.13   $46.15   $46.10  
  Purchase #6 $158.27   8.753%   $172.1234   $172.12   $172.10   $172.10  
  Purchase #7 $155.85   4.341%   $162.6154   $162.62   $162.60   $162.60  
  7 purchase totals = $1,093.23       $1,199.3122   $1,199.31   $1,199.30   $1,199.20