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	$216.28	8.295%	$234.2204	$234.22	$234.20	$234.20
Purchase #2	$226.49	9.709%	$248.4799	$248.48	$248.50	$248.50
Purchase #3	$176.72	13.566%	$200.6938	$200.69	$200.70	$200.70
Purchase #4	$213.79	7.476%	$229.7729	$229.77	$229.75	$229.80
Purchase #5	$90.61	13.251%	$102.6167	$102.62	$102.60	$102.60
Purchase #6	$101.69	3.859%	$105.6142	$105.61	$105.60	$105.60
Purchase #7	$52.38	3.597%	$54.2641	$54.26	$54.25	$54.30
7 purchase totals =	$1,077.96		$1,175.6620	$1,175.65	$1,175.60	$1,175.70