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	$162.30	6.600%	$173.0118	$173.01	$173.00	$173.00
Purchase #2	$165.62	3.532%	$171.4697	$171.47	$171.45	$171.50
Purchase #3	$13.26	13.790%	$15.0886	$15.09	$15.10	$15.10
Purchase #4	$159.70	9.510%	$174.8875	$174.89	$174.90	$174.90
Purchase #5	$108.63	3.583%	$112.5222	$112.52	$112.50	$112.50
Purchase #6	$140.78	6.572%	$150.0321	$150.03	$150.05	$150.00
Purchase #7	$204.83	10.222%	$225.7677	$225.77	$225.75	$225.80
7 purchase totals =	$955.12		$1,022.7796	$1,022.78	$1,022.75	$1,022.80