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	$66.97	5.768%	$70.8328	$70.83	$70.85	$70.80
Purchase #2	$104.51	12.377%	$117.4452	$117.45	$117.45	$117.40
Purchase #3	$93.28	7.829%	$100.5829	$100.58	$100.60	$100.60
Purchase #4	$118.69	6.625%	$126.5532	$126.55	$126.55	$126.60
Purchase #5	$174.36	9.591%	$191.0829	$191.08	$191.10	$191.10
Purchase #6	$196.31	13.251%	$222.323	$222.32	$222.30	$222.30
Purchase #7	$155.64	6.516%	$165.7815	$165.78	$165.80	$165.80
7 purchase totals =	$909.76		$994.6015	$994.59	$994.65	$994.60