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	$238.75	3.784%	$247.7843	$247.78	$247.80	$247.80
Purchase #2	$52.45	10.488%	$57.951	$57.95	$57.95	$58.00
Purchase #3	$167.90	7.552%	$180.5798	$180.58	$180.60	$180.60
Purchase #4	$90.84	5.722%	$96.0379	$96.04	$96.05	$96.00
Purchase #5	$78.95	8.323%	$85.521	$85.52	$85.50	$85.50
Purchase #6	$233.78	7.796%	$252.0055	$252.01	$252.00	$252.00
Purchase #7	$179.72	5.413%	$189.4482	$189.45	$189.45	$189.40
7 purchase totals =	$1,042.39		$1,109.3277	$1,109.33	$1,109.35	$1,109.30