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 $239.45   11.574%   $267.1639   $267.16   $267.15   $267.20  
  Purchase #2 $206.55   13.250%   $233.9179   $233.92   $233.90   $233.90  
  Purchase #3 $185.25   6.424%   $197.1505   $197.15   $197.15   $197.20  
  Purchase #4 $91.94   3.777%   $95.4126   $95.41   $95.40   $95.40  
  Purchase #5 $149.53   13.121%   $169.1498   $169.15   $169.15   $169.10  
  Purchase #6 $187.50   7.713%   $201.9619   $201.96   $201.95   $202.00  
  Purchase #7 $215.86   7.147%   $231.2875   $231.29   $231.30   $231.30  
  7 purchase totals = $1,276.08       $1,396.0441   $1,396.04   $1,396.00   $1,396.10