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	$50.65	11.271%	$56.3588	$56.36	$56.35	$56.40
Purchase #2	$107.69	3.637%	$111.6067	$111.61	$111.60	$111.60
Purchase #3	$175.69	3.243%	$181.3876	$181.39	$181.40	$181.40
Purchase #4	$174.30	5.808%	$184.4233	$184.42	$184.40	$184.40
Purchase #5	$7.91	11.599%	$8.8275	$8.83	$8.85	$8.80
Purchase #6	$165.58	3.716%	$171.733	$171.73	$171.75	$171.70
Purchase #7	$44.70	3.463%	$46.248	$46.25	$46.25	$46.20
7 purchase totals =	$726.52		$760.5849	$760.59	$760.60	$760.50