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	$172.72	9.511%	$189.1474	$189.15	$189.15	$189.10
Purchase #2	$99.43	10.425%	$109.7956	$109.80	$109.80	$109.80
Purchase #3	$87.26	3.172%	$90.0279	$90.03	$90.05	$90.00
Purchase #4	$170.45	12.118%	$191.1051	$191.11	$191.10	$191.10
Purchase #5	$134.50	5.864%	$142.3871	$142.39	$142.40	$142.40
Purchase #6	$124.93	7.635%	$134.4684	$134.47	$134.45	$134.50
Purchase #7	$158.64	4.326%	$165.5028	$165.50	$165.50	$165.50
7 purchase totals =	$947.93		$1,022.4343	$1,022.45	$1,022.45	$1,022.40