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	$170.92	10.827%	$189.4255	$189.43	$189.45	$189.40
Purchase #2	$124.73	3.121%	$128.6228	$128.62	$128.60	$128.60
Purchase #3	$227.49	11.710%	$254.1291	$254.13	$254.15	$254.10
Purchase #4	$145.75	3.823%	$151.322	$151.32	$151.30	$151.30
Purchase #5	$59.88	3.235%	$61.8171	$61.82	$61.80	$61.80
Purchase #6	$116.75	5.603%	$123.2915	$123.29	$123.30	$123.30
Purchase #7	$176.45	4.774%	$184.8737	$184.87	$184.85	$184.90
7 purchase totals =	$1,021.97		$1,093.4817	$1,093.48	$1,093.45	$1,093.40