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	$233.54	9.673%	$256.1303	$256.13	$256.15	$256.10
Purchase #2	$172.77	7.234%	$185.2682	$185.27	$185.25	$185.30
Purchase #3	$147.92	6.792%	$157.9667	$157.97	$157.95	$158.00
Purchase #4	$127.67	12.294%	$143.3657	$143.37	$143.35	$143.40
Purchase #5	$38.39	10.717%	$42.5043	$42.50	$42.50	$42.50
Purchase #6	$49.36	7.425%	$53.025	$53.03	$53.05	$53.00
Purchase #7	$195.85	9.159%	$213.7879	$213.79	$213.80	$213.80
7 purchase totals =	$965.50		$1,052.0481	$1,052.06	$1,052.05	$1,052.10