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	$147.56	7.394%	$158.4706	$158.47	$158.45	$158.50
Purchase #2	$36.65	6.853%	$39.1616	$39.16	$39.15	$39.20
Purchase #3	$99.69	11.412%	$111.0666	$111.07	$111.05	$111.10
Purchase #4	$82.81	4.484%	$86.5232	$86.52	$86.50	$86.50
Purchase #5	$37.65	13.668%	$42.796	$42.80	$42.80	$42.80
Purchase #6	$13.99	9.460%	$15.3135	$15.31	$15.30	$15.30
Purchase #7	$81.56	9.695%	$89.4672	$89.47	$89.45	$89.50
7 purchase totals =	$499.91		$542.7987	$542.80	$542.70	$542.90