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	$111.88	5.723%	$118.2829	$118.28	$118.30	$118.30
Purchase #2	$64.40	10.333%	$71.0545	$71.05	$71.05	$71.10
Purchase #3	$131.33	5.105%	$138.0344	$138.03	$138.05	$138.00
Purchase #4	$195.66	6.570%	$208.5149	$208.51	$208.50	$208.50
Purchase #5	$214.39	7.181%	$229.7853	$229.79	$229.80	$229.80
Purchase #6	$131.37	4.363%	$137.1017	$137.10	$137.10	$137.10
Purchase #7	$120.62	5.646%	$127.4302	$127.43	$127.45	$127.40
7 purchase totals =	$969.65		$1,030.2039	$1,030.19	$1,030.25	$1,030.20