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 $91.84   5.530%   $96.9188   $96.92   $96.90   $96.90  
  Purchase #2 $205.67   4.106%   $214.1148   $214.11   $214.10   $214.10  
  Purchase #3 $202.57   5.784%   $214.2866   $214.29   $214.30   $214.30  
  Purchase #4 $56.90   3.644%   $58.9734   $58.97   $58.95   $59.00  
  Purchase #5 $223.73   4.825%   $234.525   $234.53   $234.55   $234.50  
  Purchase #6 $107.69   9.739%   $118.1779   $118.18   $118.20   $118.20  
  Purchase #7 $177.80   6.157%   $188.7471   $188.75   $188.75   $188.70  
  7 purchase totals = $1,066.20       $1,125.7436   $1,125.75   $1,125.75   $1,125.70