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	$151.44	3.192%	$156.274	$156.27	$156.25	$156.30
Purchase #2	$222.29	10.448%	$245.5149	$245.51	$245.50	$245.50
Purchase #3	$145.84	12.637%	$164.2698	$164.27	$164.25	$164.30
Purchase #4	$18.57	6.307%	$19.7412	$19.74	$19.75	$19.70
Purchase #5	$221.42	8.452%	$240.1344	$240.13	$240.15	$240.10
Purchase #6	$137.92	6.342%	$146.6669	$146.67	$146.65	$146.70
Purchase #7	$155.52	10.688%	$172.142	$172.14	$172.15	$172.10
7 purchase totals =	$1,053.00		$1,144.7432	$1,144.73	$1,144.70	$1,144.70