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	$169.82	8.434%	$184.1426	$184.14	$184.15	$184.10
Purchase #2	$207.56	11.786%	$232.023	$232.02	$232.00	$232.00
Purchase #3	$161.27	4.104%	$167.8885	$167.89	$167.90	$167.90
Purchase #4	$85.56	5.815%	$90.5353	$90.54	$90.55	$90.50
Purchase #5	$49.77	6.563%	$53.0364	$53.04	$53.05	$53.00
Purchase #6	$158.95	8.697%	$172.7739	$172.77	$172.75	$172.80
Purchase #7	$219.67	13.301%	$248.8883	$248.89	$248.90	$248.90
7 purchase totals =	$1,052.60		$1,149.2880	$1,149.29	$1,149.30	$1,149.20