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	$205.43	12.516%	$231.1416	$231.14	$231.15	$231.10
Purchase #2	$135.32	9.417%	$148.0631	$148.06	$148.05	$148.10
Purchase #3	$59.38	3.478%	$61.4452	$61.45	$61.45	$61.40
Purchase #4	$33.74	9.608%	$36.9817	$36.98	$37.00	$37.00
Purchase #5	$118.29	8.146%	$127.9259	$127.93	$127.95	$127.90
Purchase #6	$154.70	11.121%	$171.9042	$171.90	$171.90	$171.90
Purchase #7	$98.52	10.735%	$109.0961	$109.10	$109.10	$109.10
7 purchase totals =	$805.38		$886.5578	$886.56	$886.60	$886.50