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	$88.86	4.269%	$92.6534	$92.65	$92.65	$92.70
Purchase #2	$216.43	12.740%	$244.0032	$244.00	$244.00	$244.00
Purchase #3	$50.89	4.702%	$53.2828	$53.28	$53.30	$53.30
Purchase #4	$129.29	12.298%	$145.1901	$145.19	$145.20	$145.20
Purchase #5	$46.95	4.130%	$48.889	$48.89	$48.90	$48.90
Purchase #6	$138.56	5.705%	$146.4648	$146.46	$146.45	$146.50
Purchase #7	$149.78	13.376%	$169.8146	$169.81	$169.80	$169.80
7 purchase totals =	$820.76		$900.2979	$900.28	$900.30	$900.40