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	$100.32	5.421%	$105.7583	$105.76	$105.75	$105.80
Purchase #2	$181.70	12.373%	$204.1817	$204.18	$204.20	$204.20
Purchase #3	$120.99	4.531%	$126.4721	$126.47	$126.45	$126.50
Purchase #4	$127.91	10.749%	$141.659	$141.66	$141.65	$141.70
Purchase #5	$184.92	13.148%	$209.2333	$209.23	$209.25	$209.20
Purchase #6	$67.76	5.688%	$71.6142	$71.61	$71.60	$71.60
Purchase #7	$211.35	5.520%	$223.0165	$223.02	$223.00	$223.00
7 purchase totals =	$994.95		$1,081.9351	$1,081.93	$1,081.90	$1,082.00