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	$41.38	11.343%	$46.0737	$46.07	$46.05	$46.10
Purchase #2	$30.65	13.357%	$34.7439	$34.74	$34.75	$34.70
Purchase #3	$155.91	6.295%	$165.7245	$165.72	$165.70	$165.70
Purchase #4	$99.58	5.310%	$104.8677	$104.87	$104.85	$104.90
Purchase #5	$178.31	11.123%	$198.1434	$198.14	$198.15	$198.10
Purchase #6	$20.28	5.228%	$21.3402	$21.34	$21.35	$21.30
Purchase #7	$91.67	8.851%	$99.7837	$99.78	$99.80	$99.80
7 purchase totals =	$617.78		$670.6771	$670.66	$670.65	$670.60