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	$101.94	8.206%	$110.3052	$110.31	$110.30	$110.30
Purchase #2	$48.76	7.215%	$52.278	$52.28	$52.30	$52.30
Purchase #3	$53.80	13.713%	$61.1776	$61.18	$61.20	$61.20
Purchase #4	$35.60	5.654%	$37.6128	$37.61	$37.60	$37.60
Purchase #5	$59.79	9.410%	$65.4162	$65.42	$65.40	$65.40
Purchase #6	$249.64	5.695%	$263.857	$263.86	$263.85	$263.90
Purchase #7	$88.90	8.726%	$96.6574	$96.66	$96.65	$96.70
7 purchase totals =	$638.43		$687.3042	$687.32	$687.30	$687.40