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	$138.48	12.250%	$155.4438	$155.44	$155.45	$155.40
Purchase #2	$158.33	9.551%	$173.4521	$173.45	$173.45	$173.50
Purchase #3	$42.54	11.623%	$47.4844	$47.48	$47.50	$47.50
Purchase #4	$169.29	6.229%	$179.8351	$179.84	$179.85	$179.80
Purchase #5	$92.49	5.678%	$97.7416	$97.74	$97.75	$97.70
Purchase #6	$202.52	8.444%	$219.6208	$219.62	$219.60	$219.60
Purchase #7	$174.38	7.659%	$187.7358	$187.74	$187.75	$187.70
7 purchase totals =	$978.03		$1,061.3136	$1,061.31	$1,061.35	$1,061.20