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	$143.87	3.443%	$148.8234	$148.82	$148.80	$148.80
Purchase #2	$82.99	13.322%	$94.0459	$94.05	$94.05	$94.00
Purchase #3	$140.75	9.714%	$154.4225	$154.42	$154.40	$154.40
Purchase #4	$6.88	8.395%	$7.4576	$7.46	$7.45	$7.50
Purchase #5	$41.83	4.346%	$43.6479	$43.65	$43.65	$43.60
Purchase #6	$82.77	10.834%	$91.7373	$91.74	$91.75	$91.70
Purchase #7	$75.61	3.873%	$78.5384	$78.54	$78.55	$78.50
7 purchase totals =	$574.70		$618.6730	$618.68	$618.65	$618.50