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	$166.43	10.767%	$184.3495	$184.35	$184.35	$184.30
Purchase #2	$217.66	9.389%	$238.0961	$238.10	$238.10	$238.10
Purchase #3	$182.92	6.194%	$194.2501	$194.25	$194.25	$194.30
Purchase #4	$152.73	4.322%	$159.331	$159.33	$159.35	$159.30
Purchase #5	$75.88	5.497%	$80.0511	$80.05	$80.05	$80.10
Purchase #6	$152.71	8.370%	$165.4918	$165.49	$165.50	$165.50
Purchase #7	$60.60	7.585%	$65.1965	$65.20	$65.20	$65.20
7 purchase totals =	$1,008.93		$1,086.7661	$1,086.77	$1,086.80	$1,086.80