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	$94.76	4.332%	$98.865	$98.87	$98.85	$98.90
Purchase #2	$55.89	11.199%	$62.1491	$62.15	$62.15	$62.10
Purchase #3	$21.83	3.434%	$22.5796	$22.58	$22.60	$22.60
Purchase #4	$82.35	5.442%	$86.8315	$86.83	$86.85	$86.80
Purchase #5	$190.92	3.836%	$198.2437	$198.24	$198.25	$198.20
Purchase #6	$42.64	7.675%	$45.9126	$45.91	$45.90	$45.90
Purchase #7	$231.27	13.327%	$262.0914	$262.09	$262.10	$262.10
7 purchase totals =	$719.66		$776.6729	$776.67	$776.70	$776.60