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	$142.30	4.631%	$148.8899	$148.89	$148.90	$148.90
Purchase #2	$91.28	7.696%	$98.3049	$98.30	$98.30	$98.30
Purchase #3	$155.63	4.596%	$162.7828	$162.78	$162.80	$162.80
Purchase #4	$79.91	12.467%	$89.8724	$89.87	$89.85	$89.90
Purchase #5	$102.60	8.547%	$111.3692	$111.37	$111.35	$111.40
Purchase #6	$146.64	13.447%	$166.3587	$166.36	$166.35	$166.40
Purchase #7	$154.37	7.341%	$165.7023	$165.70	$165.70	$165.70
7 purchase totals =	$872.73		$943.2802	$943.27	$943.25	$943.40