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	$174.55	3.214%	$180.16	$180.16	$180.15	$180.20
Purchase #2	$136.25	6.865%	$145.6036	$145.60	$145.60	$145.60
Purchase #3	$229.35	8.867%	$249.6865	$249.69	$249.70	$249.70
Purchase #4	$182.77	4.321%	$190.6675	$190.67	$190.65	$190.70
Purchase #5	$36.50	13.446%	$41.4078	$41.41	$41.40	$41.40
Purchase #6	$34.56	8.793%	$37.5989	$37.60	$37.60	$37.60
Purchase #7	$59.95	3.643%	$62.134	$62.13	$62.15	$62.10
7 purchase totals =	$853.93		$907.2583	$907.26	$907.25	$907.30