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 $244.51   9.434%   $267.5771   $267.58   $267.60   $267.60  
  Purchase #2 $161.58   8.551%   $175.3967   $175.40   $175.40   $175.40  
  Purchase #3 $151.30   10.642%   $167.4013   $167.40   $167.40   $167.40  
  Purchase #4 $123.27   8.297%   $133.4977   $133.50   $133.50   $133.50  
  Purchase #5 $211.31   9.711%   $231.8303   $231.83   $231.85   $231.80  
  Purchase #6 $148.64   13.773%   $169.1122   $169.11   $169.10   $169.10  
  Purchase #7 $37.35   10.147%   $41.1399   $41.14   $41.15   $41.10  
  7 purchase totals = $1,077.96       $1,185.9552   $1,185.96   $1,186.00   $1,185.90