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	$74.81	10.378%	$82.5738	$82.57	$82.55	$82.60
Purchase #2	$75.97	12.103%	$85.1646	$85.16	$85.15	$85.20
Purchase #3	$52.57	6.783%	$56.1358	$56.14	$56.15	$56.10
Purchase #4	$55.85	12.239%	$62.6855	$62.69	$62.70	$62.70
Purchase #5	$80.75	13.328%	$91.5124	$91.51	$91.50	$91.50
Purchase #6	$98.50	7.459%	$105.8471	$105.85	$105.85	$105.80
Purchase #7	$80.91	3.304%	$83.5833	$83.58	$83.60	$83.60
7 purchase totals =	$519.36		$567.5025	$567.50	$567.50	$567.50