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	$33.58	5.536%	$35.439	$35.44	$35.45	$35.40
Purchase #2	$18.69	4.177%	$19.4707	$19.47	$19.45	$19.50
Purchase #3	$5.89	11.238%	$6.5519	$6.55	$6.55	$6.60
Purchase #4	$69.79	4.378%	$72.8454	$72.85	$72.85	$72.80
Purchase #5	$56.41	13.306%	$63.9159	$63.92	$63.90	$63.90
Purchase #6	$245.81	3.858%	$255.2933	$255.29	$255.30	$255.30
Purchase #7	$205.55	5.273%	$216.3887	$216.39	$216.40	$216.40
7 purchase totals =	$635.72		$669.9049	$669.91	$669.90	$669.90