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	$6.95	3.594%	$7.1998	$7.20	$7.20	$7.20
Purchase #2	$210.49	7.107%	$225.4495	$225.45	$225.45	$225.40
Purchase #3	$145.63	6.608%	$155.2532	$155.25	$155.25	$155.30
Purchase #4	$69.52	13.207%	$78.7015	$78.70	$78.70	$78.70
Purchase #5	$124.37	10.420%	$137.3294	$137.33	$137.35	$137.30
Purchase #6	$144.35	4.872%	$151.3827	$151.38	$151.40	$151.40
Purchase #7	$231.99	10.748%	$256.9243	$256.92	$256.90	$256.90
7 purchase totals =	$933.30		$1,012.2404	$1,012.23	$1,012.25	$1,012.20