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	$147.69	12.149%	$165.6329	$165.63	$165.65	$165.60
Purchase #2	$187.78	6.504%	$199.9932	$199.99	$200.00	$200.00
Purchase #3	$72.82	12.658%	$82.0376	$82.04	$82.05	$82.00
Purchase #4	$17.54	9.205%	$19.1546	$19.15	$19.15	$19.20
Purchase #5	$35.79	11.362%	$39.8565	$39.86	$39.85	$39.90
Purchase #6	$44.40	12.752%	$50.0619	$50.06	$50.05	$50.10
Purchase #7	$41.49	7.778%	$44.7171	$44.72	$44.70	$44.70
7 purchase totals =	$547.51		$601.4538	$601.45	$601.45	$601.50