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	$228.86	11.506%	$255.1926	$255.19	$255.20	$255.20
Purchase #2	$223.80	5.672%	$236.4939	$236.49	$236.50	$236.50
Purchase #3	$62.65	8.149%	$67.7553	$67.76	$67.75	$67.80
Purchase #4	$57.50	13.680%	$65.366	$65.37	$65.35	$65.40
Purchase #5	$209.61	13.137%	$237.1465	$237.15	$237.15	$237.10
Purchase #6	$116.90	11.505%	$130.3493	$130.35	$130.35	$130.30
Purchase #7	$20.57	7.749%	$22.164	$22.16	$22.15	$22.20
7 purchase totals =	$919.89		$1,014.4676	$1,014.47	$1,014.45	$1,014.50