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	$160.83	10.212%	$177.254	$177.25	$177.25	$177.30
Purchase #2	$149.66	5.776%	$158.3044	$158.30	$158.30	$158.30
Purchase #3	$191.42	13.807%	$217.8494	$217.85	$217.85	$217.80
Purchase #4	$96.90	6.480%	$103.1791	$103.18	$103.20	$103.20
Purchase #5	$226.58	4.553%	$236.8962	$236.90	$236.90	$236.90
Purchase #6	$92.90	11.485%	$103.5696	$103.57	$103.55	$103.60
Purchase #7	$7.56	3.251%	$7.8058	$7.81	$7.80	$7.80
7 purchase totals =	$925.85		$1,004.8585	$1,004.86	$1,004.85	$1,004.90