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	$196.69	6.519%	$209.5122	$209.51	$209.50	$209.50
Purchase #2	$65.72	13.345%	$74.4903	$74.49	$74.50	$74.50
Purchase #3	$168.61	4.160%	$175.6242	$175.62	$175.60	$175.60
Purchase #4	$202.60	13.159%	$229.2601	$229.26	$229.25	$229.30
Purchase #5	$117.88	10.706%	$130.5002	$130.50	$130.50	$130.50
Purchase #6	$6.92	13.861%	$7.8792	$7.88	$7.90	$7.90
Purchase #7	$236.51	8.303%	$256.1474	$256.15	$256.15	$256.10
7 purchase totals =	$994.93		$1,083.4136	$1,083.41	$1,083.40	$1,083.40