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	$162.92	9.324%	$178.1107	$178.11	$178.10	$178.10
Purchase #2	$75.43	4.438%	$78.7776	$78.78	$78.80	$78.80
Purchase #3	$183.83	5.410%	$193.7752	$193.78	$193.80	$193.80
Purchase #4	$16.35	11.488%	$18.2283	$18.23	$18.25	$18.20
Purchase #5	$98.57	12.680%	$111.0687	$111.07	$111.05	$111.10
Purchase #6	$229.49	10.557%	$253.7173	$253.72	$253.70	$253.70
Purchase #7	$149.89	11.316%	$166.8516	$166.85	$166.85	$166.90
7 purchase totals =	$916.48		$1,000.5294	$1,000.54	$1,000.55	$1,000.60