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	$77.28	4.133%	$80.474	$80.47	$80.45	$80.50
Purchase #2	$14.35	10.784%	$15.8975	$15.90	$15.90	$15.90
Purchase #3	$154.71	7.262%	$165.945	$165.95	$165.95	$165.90
Purchase #4	$221.75	3.378%	$229.2407	$229.24	$229.25	$229.20
Purchase #5	$92.74	7.359%	$99.5647	$99.56	$99.55	$99.60
Purchase #6	$211.31	6.506%	$225.0578	$225.06	$225.05	$225.10
Purchase #7	$141.62	12.183%	$158.8736	$158.87	$158.85	$158.90
7 purchase totals =	$913.76		$975.0533	$975.05	$975.00	$975.10