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	$120.88	13.836%	$137.605	$137.61	$137.60	$137.60
Purchase #2	$188.73	7.355%	$202.6111	$202.61	$202.60	$202.60
Purchase #3	$158.85	8.723%	$172.7065	$172.71	$172.70	$172.70
Purchase #4	$186.84	12.815%	$210.7835	$210.78	$210.80	$210.80
Purchase #5	$180.63	13.463%	$204.9482	$204.95	$204.95	$204.90
Purchase #6	$9.59	5.194%	$10.0881	$10.09	$10.10	$10.10
Purchase #7	$58.77	6.476%	$62.5759	$62.58	$62.60	$62.60
7 purchase totals =	$904.29		$1,001.3183	$1,001.33	$1,001.35	$1,001.30