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	$165.88	5.549%	$175.0847	$175.08	$175.10	$175.10
Purchase #2	$5.31	7.453%	$5.7058	$5.71	$5.70	$5.70
Purchase #3	$98.54	13.109%	$111.4576	$111.46	$111.45	$111.50
Purchase #4	$49.35	9.489%	$54.0328	$54.03	$54.05	$54.00
Purchase #5	$212.91	6.815%	$227.4198	$227.42	$227.40	$227.40
Purchase #6	$144.66	11.592%	$161.429	$161.43	$161.45	$161.40
Purchase #7	$244.69	10.755%	$271.0064	$271.01	$271.00	$271.00
7 purchase totals =	$921.34		$1,006.1361	$1,006.14	$1,006.15	$1,006.10