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 $181.60   11.486%   $202.4586   $202.46   $202.45   $202.50  
  Purchase #2 $240.95   8.136%   $260.5537   $260.55   $260.55   $260.60  
  Purchase #3 $181.38   8.622%   $197.0186   $197.02   $197.00   $197.00  
  Purchase #4 $245.44   12.277%   $275.5727   $275.57   $275.55   $275.60  
  Purchase #5 $153.43   10.139%   $168.9863   $168.99   $169.00   $169.00  
  Purchase #6 $172.30   11.796%   $192.6245   $192.62   $192.60   $192.60  
  Purchase #7 $68.53   5.132%   $72.047   $72.05   $72.05   $72.00  
  7 purchase totals = $1,243.63       $1,369.2614   $1,369.26   $1,369.20   $1,369.30