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 $141.92   8.261%   $153.644   $153.64   $153.65   $153.60  
  Purchase #2 $241.85   7.104%   $259.031   $259.03   $259.05   $259.00  
  Purchase #3 $234.41   5.230%   $246.6696   $246.67   $246.65   $246.70  
  Purchase #4 $129.33   13.752%   $147.1155   $147.12   $147.10   $147.10  
  Purchase #5 $126.36   5.364%   $133.138   $133.14   $133.15   $133.10  
  Purchase #6 $142.65   6.489%   $151.9066   $151.91   $151.90   $151.90  
  Purchase #7 $30.82   4.784%   $32.2944   $32.29   $32.30   $32.30  
  7 purchase totals = $1,047.34       $1,123.7991   $1,123.80   $1,123.80   $1,123.70