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	$249.30	9.325%	$272.5472	$272.55	$272.55	$272.50
Purchase #2	$60.61	11.592%	$67.6359	$67.64	$67.65	$67.60
Purchase #3	$46.76	10.210%	$51.5342	$51.53	$51.55	$51.50
Purchase #4	$194.62	8.139%	$210.4601	$210.46	$210.45	$210.50
Purchase #5	$34.95	7.648%	$37.623	$37.62	$37.60	$37.60
Purchase #6	$201.66	4.788%	$211.3155	$211.32	$211.30	$211.30
Purchase #7	$246.57	3.114%	$254.2482	$254.25	$254.25	$254.20
7 purchase totals =	$1,034.47		$1,105.3641	$1,105.37	$1,105.35	$1,105.20