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	$9.60	5.258%	$10.1048	$10.10	$10.10	$10.10
Purchase #2	$94.58	5.250%	$99.5455	$99.55	$99.55	$99.50
Purchase #3	$230.64	11.402%	$256.9376	$256.94	$256.95	$256.90
Purchase #4	$26.48	12.280%	$29.7317	$29.73	$29.75	$29.70
Purchase #5	$127.45	12.519%	$143.4055	$143.41	$143.40	$143.40
Purchase #6	$238.25	6.836%	$254.5368	$254.54	$254.55	$254.50
Purchase #7	$204.81	5.367%	$215.8022	$215.80	$215.80	$215.80
7 purchase totals =	$931.81		$1,010.0641	$1,010.07	$1,010.10	$1,009.90