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	$44.59	3.367%	$46.0913	$46.09	$46.10	$46.10
Purchase #2	$120.73	5.838%	$127.7782	$127.78	$127.80	$127.80
Purchase #3	$219.51	8.584%	$238.3527	$238.35	$238.35	$238.40
Purchase #4	$62.59	12.514%	$70.4225	$70.42	$70.40	$70.40
Purchase #5	$28.27	4.665%	$29.5888	$29.59	$29.60	$29.60
Purchase #6	$222.27	10.507%	$245.6239	$245.62	$245.60	$245.60
Purchase #7	$111.64	5.806%	$118.1218	$118.12	$118.10	$118.10
7 purchase totals =	$809.60		$875.9792	$875.97	$875.95	$876.00