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	$74.50	4.377%	$77.7609	$77.76	$77.75	$77.80
Purchase #2	$172.77	8.685%	$187.7751	$187.78	$187.80	$187.80
Purchase #3	$243.77	5.556%	$257.3139	$257.31	$257.30	$257.30
Purchase #4	$93.72	12.741%	$105.6609	$105.66	$105.65	$105.70
Purchase #5	$105.37	7.174%	$112.9292	$112.93	$112.95	$112.90
Purchase #6	$111.95	10.672%	$123.8973	$123.90	$123.90	$123.90
Purchase #7	$144.25	9.505%	$157.961	$157.96	$157.95	$158.00
7 purchase totals =	$946.33		$1,023.2983	$1,023.30	$1,023.30	$1,023.40