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	$146.82	7.417%	$157.7096	$157.71	$157.70	$157.70
Purchase #2	$196.50	9.506%	$215.1793	$215.18	$215.20	$215.20
Purchase #3	$49.90	7.143%	$53.4644	$53.46	$53.45	$53.50
Purchase #4	$180.75	3.530%	$187.1305	$187.13	$187.15	$187.10
Purchase #5	$206.86	3.581%	$214.2677	$214.27	$214.25	$214.30
Purchase #6	$34.76	12.472%	$39.0953	$39.10	$39.10	$39.10
Purchase #7	$142.35	6.468%	$151.5572	$151.56	$151.55	$151.60
7 purchase totals =	$957.94		$1,018.4040	$1,018.41	$1,018.40	$1,018.50