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	$92.94	12.739%	$104.7796	$104.78	$104.80	$104.80
Purchase #2	$235.71	8.257%	$255.1726	$255.17	$255.15	$255.20
Purchase #3	$91.60	5.503%	$96.6407	$96.64	$96.65	$96.60
Purchase #4	$242.30	8.319%	$262.4569	$262.46	$262.45	$262.50
Purchase #5	$27.92	13.456%	$31.6769	$31.68	$31.70	$31.70
Purchase #6	$46.47	13.231%	$52.6184	$52.62	$52.60	$52.60
Purchase #7	$214.43	13.219%	$242.7755	$242.78	$242.80	$242.80
7 purchase totals =	$951.37		$1,046.1206	$1,046.13	$1,046.15	$1,046.20