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	$198.39	12.128%	$222.4507	$222.45	$222.45	$222.50
Purchase #2	$37.33	9.434%	$40.8517	$40.85	$40.85	$40.90
Purchase #3	$239.41	11.396%	$266.6932	$266.69	$266.70	$266.70
Purchase #4	$109.88	7.734%	$118.3781	$118.38	$118.40	$118.40
Purchase #5	$164.39	5.166%	$172.8824	$172.88	$172.90	$172.90
Purchase #6	$136.90	11.590%	$152.7667	$152.77	$152.75	$152.80
Purchase #7	$66.64	7.714%	$71.7806	$71.78	$71.80	$71.80
7 purchase totals =	$952.94		$1,045.8034	$1,045.80	$1,045.85	$1,046.00