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	$208.83	3.198%	$215.5084	$215.51	$215.50	$215.50
Purchase #2	$250.64	11.531%	$279.5413	$279.54	$279.55	$279.50
Purchase #3	$59.88	7.621%	$64.4435	$64.44	$64.45	$64.40
Purchase #4	$226.44	5.316%	$238.4776	$238.48	$238.50	$238.50
Purchase #5	$48.82	13.687%	$55.502	$55.50	$55.50	$55.50
Purchase #6	$12.39	4.737%	$12.9769	$12.98	$13.00	$13.00
Purchase #7	$36.26	12.118%	$40.654	$40.65	$40.65	$40.70
7 purchase totals =	$843.26		$907.1037	$907.10	$907.15	$907.10