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	$76.98	6.713%	$82.1477	$82.15	$82.15	$82.10
Purchase #2	$223.57	8.139%	$241.7664	$241.77	$241.75	$241.80
Purchase #3	$232.97	9.803%	$255.808	$255.81	$255.80	$255.80
Purchase #4	$236.27	8.233%	$255.7221	$255.72	$255.70	$255.70
Purchase #5	$37.73	13.299%	$42.7477	$42.75	$42.75	$42.70
Purchase #6	$230.91	11.119%	$256.5849	$256.58	$256.60	$256.60
Purchase #7	$79.25	11.422%	$88.3019	$88.30	$88.30	$88.30
7 purchase totals =	$1,117.68		$1,223.0787	$1,223.08	$1,223.05	$1,223.00