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	$199.47	5.587%	$210.6144	$210.61	$210.60	$210.60
Purchase #2	$36.59	6.286%	$38.89	$38.89	$38.90	$38.90
Purchase #3	$191.32	12.600%	$215.4263	$215.43	$215.45	$215.40
Purchase #4	$250.68	6.232%	$266.3024	$266.30	$266.30	$266.30
Purchase #5	$236.92	3.453%	$245.1008	$245.10	$245.10	$245.10
Purchase #6	$211.74	10.331%	$233.6149	$233.61	$233.60	$233.60
Purchase #7	$48.40	8.236%	$52.3862	$52.39	$52.40	$52.40
7 purchase totals =	$1,175.12		$1,262.3350	$1,262.33	$1,262.35	$1,262.30