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	$154.60	11.501%	$172.3805	$172.38	$172.40	$172.40
Purchase #2	$96.90	8.796%	$105.4233	$105.42	$105.40	$105.40
Purchase #3	$117.26	11.861%	$131.1682	$131.17	$131.15	$131.20
Purchase #4	$136.27	4.803%	$142.815	$142.82	$142.80	$142.80
Purchase #5	$141.87	5.553%	$149.748	$149.75	$149.75	$149.70
Purchase #6	$121.56	4.344%	$126.8406	$126.84	$126.85	$126.80
Purchase #7	$156.76	13.568%	$178.0292	$178.03	$178.05	$178.00
7 purchase totals =	$925.22		$1,006.4048	$1,006.41	$1,006.40	$1,006.30