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	$85.42	6.847%	$91.2687	$91.27	$91.25	$91.30
Purchase #2	$187.39	12.549%	$210.9056	$210.91	$210.90	$210.90
Purchase #3	$83.41	7.716%	$89.8459	$89.85	$89.85	$89.80
Purchase #4	$201.49	13.419%	$228.5279	$228.53	$228.55	$228.50
Purchase #5	$222.94	13.293%	$252.5754	$252.58	$252.60	$252.60
Purchase #6	$156.29	10.244%	$172.3003	$172.30	$172.30	$172.30
Purchase #7	$18.95	4.600%	$19.8217	$19.82	$19.80	$19.80
7 purchase totals =	$955.89		$1,065.2455	$1,065.26	$1,065.25	$1,065.20