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	$159.32	13.363%	$180.6099	$180.61	$180.60	$180.60
Purchase #2	$196.51	3.473%	$203.3348	$203.33	$203.35	$203.30
Purchase #3	$189.45	5.845%	$200.5234	$200.52	$200.50	$200.50
Purchase #4	$41.62	3.334%	$43.0076	$43.01	$43.00	$43.00
Purchase #5	$58.95	7.162%	$63.172	$63.17	$63.15	$63.20
Purchase #6	$250.29	10.377%	$276.2626	$276.26	$276.25	$276.30
Purchase #7	$127.37	4.599%	$133.2277	$133.23	$133.25	$133.20
7 purchase totals =	$1,023.51		$1,100.1380	$1,100.13	$1,100.10	$1,100.10