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	$99.55	8.538%	$108.0496	$108.05	$108.05	$108.00
Purchase #2	$224.42	6.295%	$238.5472	$238.55	$238.55	$238.50
Purchase #3	$129.25	12.130%	$144.928	$144.93	$144.95	$144.90
Purchase #4	$48.82	12.218%	$54.7848	$54.78	$54.80	$54.80
Purchase #5	$197.61	11.107%	$219.5585	$219.56	$219.55	$219.60
Purchase #6	$71.91	6.251%	$76.4051	$76.41	$76.40	$76.40
Purchase #7	$100.28	11.244%	$111.5555	$111.56	$111.55	$111.60
7 purchase totals =	$871.84		$953.8287	$953.84	$953.85	$953.80