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	$183.52	13.593%	$208.4659	$208.47	$208.45	$208.50
Purchase #2	$134.83	5.168%	$141.798	$141.80	$141.80	$141.80
Purchase #3	$27.38	3.399%	$28.3106	$28.31	$28.30	$28.30
Purchase #4	$48.28	4.608%	$50.5047	$50.50	$50.50	$50.50
Purchase #5	$217.45	7.534%	$233.8327	$233.83	$233.85	$233.80
Purchase #6	$211.46	11.690%	$236.1797	$236.18	$236.20	$236.20
Purchase #7	$153.88	3.118%	$158.678	$158.68	$158.70	$158.70
7 purchase totals =	$976.80		$1,057.7696	$1,057.77	$1,057.80	$1,057.80