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	$100.92	4.697%	$105.6602	$105.66	$105.65	$105.70
Purchase #2	$9.33	8.793%	$10.1504	$10.15	$10.15	$10.20
Purchase #3	$82.31	10.758%	$91.1649	$91.16	$91.15	$91.20
Purchase #4	$54.96	9.104%	$59.9636	$59.96	$59.95	$60.00
Purchase #5	$47.25	11.127%	$52.5075	$52.51	$52.50	$52.50
Purchase #6	$88.64	3.453%	$91.7007	$91.70	$91.70	$91.70
Purchase #7	$173.45	12.836%	$195.714	$195.71	$195.70	$195.70
7 purchase totals =	$556.86		$606.8613	$606.85	$606.80	$607.00