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	$55.37	5.243%	$58.273	$58.27	$58.25	$58.30
Purchase #2	$63.44	12.202%	$71.1809	$71.18	$71.20	$71.20
Purchase #3	$105.42	5.722%	$111.4521	$111.45	$111.45	$111.50
Purchase #4	$231.83	7.471%	$249.15	$249.15	$249.15	$249.20
Purchase #5	$69.77	9.764%	$76.5823	$76.58	$76.60	$76.60
Purchase #6	$214.55	3.835%	$222.778	$222.78	$222.80	$222.80
Purchase #7	$228.67	9.557%	$250.524	$250.52	$250.50	$250.50
7 purchase totals =	$969.05		$1,039.9403	$1,039.93	$1,039.95	$1,040.10