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	$188.39	3.557%	$195.091	$195.09	$195.10	$195.10
Purchase #2	$92.98	8.291%	$100.689	$100.69	$100.70	$100.70
Purchase #3	$49.25	8.113%	$53.2457	$53.25	$53.25	$53.20
Purchase #4	$199.87	13.453%	$226.7585	$226.76	$226.75	$226.80
Purchase #5	$143.48	10.282%	$158.2326	$158.23	$158.25	$158.20
Purchase #6	$92.89	7.704%	$100.0462	$100.05	$100.05	$100.00
Purchase #7	$222.89	11.575%	$248.6895	$248.69	$248.70	$248.70
7 purchase totals =	$989.75		$1,082.7525	$1,082.76	$1,082.80	$1,082.70