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	$155.46	4.689%	$162.7495	$162.75	$162.75	$162.70
Purchase #2	$230.65	7.545%	$248.0525	$248.05	$248.05	$248.10
Purchase #3	$166.63	4.267%	$173.7401	$173.74	$173.75	$173.70
Purchase #4	$56.83	9.124%	$62.0152	$62.02	$62.00	$62.00
Purchase #5	$164.94	3.290%	$170.3665	$170.37	$170.35	$170.40
Purchase #6	$159.56	8.119%	$172.5147	$172.51	$172.50	$172.50
Purchase #7	$155.95	10.853%	$172.8753	$172.88	$172.90	$172.90
7 purchase totals =	$1,090.02		$1,162.3138	$1,162.32	$1,162.30	$1,162.30