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	$115.29	6.773%	$123.0986	$123.10	$123.10	$123.10
Purchase #2	$241.72	3.204%	$249.4647	$249.46	$249.45	$249.50
Purchase #3	$213.29	9.331%	$233.1921	$233.19	$233.20	$233.20
Purchase #4	$50.48	6.144%	$53.5815	$53.58	$53.60	$53.60
Purchase #5	$151.31	4.698%	$158.4185	$158.42	$158.40	$158.40
Purchase #6	$41.25	5.604%	$43.5617	$43.56	$43.55	$43.60
Purchase #7	$168.75	9.476%	$184.7408	$184.74	$184.75	$184.70
7 purchase totals =	$982.09		$1,046.0579	$1,046.05	$1,046.05	$1,046.10