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	$80.32	11.194%	$89.311	$89.31	$89.30	$89.30
Purchase #2	$200.63	11.527%	$223.7566	$223.76	$223.75	$223.80
Purchase #3	$185.47	11.812%	$207.3777	$207.38	$207.40	$207.40
Purchase #4	$47.30	3.566%	$48.9867	$48.99	$49.00	$49.00
Purchase #5	$158.77	11.182%	$176.5237	$176.52	$176.50	$176.50
Purchase #6	$47.51	5.794%	$50.2627	$50.26	$50.25	$50.30
Purchase #7	$137.73	9.552%	$150.886	$150.89	$150.90	$150.90
7 purchase totals =	$857.73		$947.1044	$947.11	$947.10	$947.20