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	$54.84	11.709%	$61.2612	$61.26	$61.25	$61.30
Purchase #2	$153.50	4.344%	$160.168	$160.17	$160.15	$160.20
Purchase #3	$223.37	13.219%	$252.8973	$252.90	$252.90	$252.90
Purchase #4	$37.74	6.710%	$40.2724	$40.27	$40.25	$40.30
Purchase #5	$161.94	13.833%	$184.3412	$184.34	$184.35	$184.30
Purchase #6	$184.65	5.218%	$194.285	$194.29	$194.30	$194.30
Purchase #7	$228.64	13.383%	$259.2389	$259.24	$259.25	$259.20
7 purchase totals =	$1,044.68		$1,152.4640	$1,152.47	$1,152.45	$1,152.50