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	$59.85	5.118%	$62.9131	$62.91	$62.90	$62.90
Purchase #2	$127.45	7.358%	$136.8278	$136.83	$136.85	$136.80
Purchase #3	$141.98	4.561%	$148.4557	$148.46	$148.45	$148.50
Purchase #4	$103.81	6.437%	$110.4922	$110.49	$110.50	$110.50
Purchase #5	$199.95	11.213%	$222.3704	$222.37	$222.35	$222.40
Purchase #6	$9.87	3.205%	$10.1863	$10.19	$10.20	$10.20
Purchase #7	$212.53	9.781%	$233.3176	$233.32	$233.30	$233.30
7 purchase totals =	$855.44		$924.5631	$924.57	$924.55	$924.60