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	$170.58	11.596%	$190.3605	$190.36	$190.35	$190.40
Purchase #2	$246.73	10.522%	$272.6909	$272.69	$272.70	$272.70
Purchase #3	$191.84	13.385%	$217.5178	$217.52	$217.50	$217.50
Purchase #4	$31.53	12.857%	$35.5838	$35.58	$35.60	$35.60
Purchase #5	$34.49	9.179%	$37.6558	$37.66	$37.65	$37.70
Purchase #6	$103.79	10.363%	$114.5458	$114.55	$114.55	$114.50
Purchase #7	$172.46	9.166%	$188.2677	$188.27	$188.25	$188.30
7 purchase totals =	$951.42		$1,056.6223	$1,056.63	$1,056.60	$1,056.70