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	$243.60	13.751%	$277.0974	$277.10	$277.10	$277.10
Purchase #2	$124.52	4.540%	$130.1732	$130.17	$130.15	$130.20
Purchase #3	$97.75	6.481%	$104.0852	$104.09	$104.10	$104.10
Purchase #4	$84.89	6.605%	$90.497	$90.50	$90.50	$90.50
Purchase #5	$217.51	12.456%	$244.603	$244.60	$244.60	$244.60
Purchase #6	$116.32	5.483%	$122.6978	$122.70	$122.70	$122.70
Purchase #7	$37.78	11.658%	$42.1844	$42.18	$42.20	$42.20
7 purchase totals =	$922.37		$1,011.3380	$1,011.34	$1,011.35	$1,011.40