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	$183.96	6.723%	$196.3276	$196.33	$196.35	$196.30
Purchase #2	$174.65	13.773%	$198.7045	$198.70	$198.70	$198.70
Purchase #3	$139.48	4.673%	$145.9979	$146.00	$146.00	$146.00
Purchase #4	$118.27	10.456%	$130.6363	$130.64	$130.65	$130.60
Purchase #5	$241.93	5.448%	$255.1103	$255.11	$255.10	$255.10
Purchase #6	$111.85	6.307%	$118.9044	$118.90	$118.90	$118.90
Purchase #7	$248.89	8.193%	$269.2816	$269.28	$269.30	$269.30
7 purchase totals =	$1,219.03		$1,314.9626	$1,314.96	$1,315.00	$1,314.90