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	$41.27	10.773%	$45.716	$45.72	$45.70	$45.70
Purchase #2	$233.28	7.431%	$250.615	$250.62	$250.60	$250.60
Purchase #3	$52.56	13.361%	$59.5825	$59.58	$59.60	$59.60
Purchase #4	$66.50	4.268%	$69.3382	$69.34	$69.35	$69.30
Purchase #5	$43.90	6.472%	$46.7412	$46.74	$46.75	$46.70
Purchase #6	$58.88	5.828%	$62.3115	$62.31	$62.30	$62.30
Purchase #7	$40.88	6.343%	$43.473	$43.47	$43.45	$43.50
7 purchase totals =	$537.27		$577.7774	$577.78	$577.75	$577.70