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	$240.49	6.237%	$255.4894	$255.49	$255.50	$255.50
Purchase #2	$30.68	7.663%	$33.031	$33.03	$33.05	$33.00
Purchase #3	$144.66	12.273%	$162.4141	$162.41	$162.40	$162.40
Purchase #4	$151.37	10.571%	$167.3713	$167.37	$167.35	$167.40
Purchase #5	$57.93	5.243%	$60.9673	$60.97	$60.95	$61.00
Purchase #6	$231.38	7.283%	$248.2314	$248.23	$248.25	$248.20
Purchase #7	$127.66	4.607%	$133.5413	$133.54	$133.55	$133.50
7 purchase totals =	$984.17		$1,061.0458	$1,061.04	$1,061.05	$1,061.00