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 $148.56   9.536%   $162.7267   $162.73   $162.75   $162.70  
  Purchase #2 $247.84   11.222%   $275.6526   $275.65   $275.65   $275.70  
  Purchase #3 $9.66   6.526%   $10.2904   $10.29   $10.30   $10.30  
  Purchase #4 $223.76   8.493%   $242.7639   $242.76   $242.75   $242.80  
  Purchase #5 $181.63   4.400%   $189.6217   $189.62   $189.60   $189.60  
  Purchase #6 $92.82   11.366%   $103.3699   $103.37   $103.35   $103.40  
  Purchase #7 $26.53   12.543%   $29.8577   $29.86   $29.85   $29.90  
  7 purchase totals = $930.80       $1,014.2829   $1,014.28   $1,014.25   $1,014.40