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	$10.27	13.616%	$11.6684	$11.67	$11.65	$11.70
Purchase #2	$137.28	10.359%	$151.5008	$151.50	$151.50	$151.50
Purchase #3	$107.98	7.465%	$116.0407	$116.04	$116.05	$116.00
Purchase #4	$115.89	13.107%	$131.0797	$131.08	$131.10	$131.10
Purchase #5	$60.41	7.632%	$65.0205	$65.02	$65.00	$65.00
Purchase #6	$91.56	8.567%	$99.4039	$99.40	$99.40	$99.40
Purchase #7	$107.31	12.639%	$120.8729	$120.87	$120.85	$120.90
7 purchase totals =	$630.70		$695.5869	$695.58	$695.55	$695.60