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	$171.43	11.348%	$190.8839	$190.88	$190.90	$190.90
Purchase #2	$9.56	11.849%	$10.6928	$10.69	$10.70	$10.70
Purchase #3	$100.46	5.289%	$105.7733	$105.77	$105.75	$105.80
Purchase #4	$219.76	10.436%	$242.6942	$242.69	$242.70	$242.70
Purchase #5	$115.94	11.172%	$128.8928	$128.89	$128.90	$128.90
Purchase #6	$143.82	9.379%	$157.3089	$157.31	$157.30	$157.30
Purchase #7	$159.54	7.404%	$171.3523	$171.35	$171.35	$171.40
7 purchase totals =	$920.51		$1,007.5982	$1,007.58	$1,007.60	$1,007.70