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	$39.31	13.413%	$44.5827	$44.58	$44.60	$44.60
Purchase #2	$194.34	8.632%	$211.1154	$211.12	$211.10	$211.10
Purchase #3	$139.71	13.463%	$158.5192	$158.52	$158.50	$158.50
Purchase #4	$123.58	3.274%	$127.626	$127.63	$127.65	$127.60
Purchase #5	$91.67	3.543%	$94.9179	$94.92	$94.90	$94.90
Purchase #6	$81.69	13.729%	$92.9052	$92.91	$92.90	$92.90
Purchase #7	$135.72	9.499%	$148.612	$148.61	$148.60	$148.60
7 purchase totals =	$806.02		$878.2784	$878.29	$878.25	$878.20