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	$191.47	6.554%	$204.0189	$204.02	$204.00	$204.00
Purchase #2	$153.44	12.453%	$172.5479	$172.55	$172.55	$172.50
Purchase #3	$143.80	4.362%	$150.0726	$150.07	$150.05	$150.10
Purchase #4	$49.49	6.391%	$52.6529	$52.65	$52.65	$52.70
Purchase #5	$43.49	4.660%	$45.5166	$45.52	$45.50	$45.50
Purchase #6	$70.54	3.675%	$73.1323	$73.13	$73.15	$73.10
Purchase #7	$194.77	11.582%	$217.3283	$217.33	$217.35	$217.30
7 purchase totals =	$847.00		$915.2695	$915.27	$915.25	$915.20