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	$172.84	13.706%	$196.5295	$196.53	$196.55	$196.50
Purchase #2	$40.36	13.405%	$45.7703	$45.77	$45.75	$45.80
Purchase #3	$19.53	7.260%	$20.9479	$20.95	$20.95	$20.90
Purchase #4	$111.99	5.755%	$118.435	$118.44	$118.45	$118.40
Purchase #5	$108.69	13.399%	$123.2534	$123.25	$123.25	$123.30
Purchase #6	$168.37	6.428%	$179.1928	$179.19	$179.20	$179.20
Purchase #7	$207.63	9.255%	$226.8462	$226.85	$226.85	$226.80
7 purchase totals =	$829.41		$910.9751	$910.98	$911.00	$910.90