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	$70.74	10.381%	$78.0835	$78.08	$78.10	$78.10
Purchase #2	$173.94	10.171%	$191.6314	$191.63	$191.65	$191.60
Purchase #3	$18.62	3.690%	$19.3071	$19.31	$19.30	$19.30
Purchase #4	$24.55	4.566%	$25.671	$25.67	$25.65	$25.70
Purchase #5	$38.64	9.563%	$42.3351	$42.34	$42.35	$42.30
Purchase #6	$87.39	4.619%	$91.4265	$91.43	$91.45	$91.40
Purchase #7	$158.62	4.206%	$165.2916	$165.29	$165.30	$165.30
7 purchase totals =	$572.50		$613.7462	$613.75	$613.80	$613.70