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	$137.46	4.373%	$143.4711	$143.47	$143.45	$143.50
Purchase #2	$227.33	6.306%	$241.6654	$241.67	$241.65	$241.70
Purchase #3	$54.36	9.605%	$59.5813	$59.58	$59.60	$59.60
Purchase #4	$6.78	5.169%	$7.1305	$7.13	$7.15	$7.10
Purchase #5	$131.54	9.516%	$144.0573	$144.06	$144.05	$144.10
Purchase #6	$46.84	8.243%	$50.701	$50.70	$50.70	$50.70
Purchase #7	$230.56	12.614%	$259.6428	$259.64	$259.65	$259.60
7 purchase totals =	$834.87		$906.2494	$906.25	$906.25	$906.30