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	$198.64	11.803%	$222.0855	$222.09	$222.10	$222.10
Purchase #2	$146.52	13.187%	$165.8416	$165.84	$165.85	$165.80
Purchase #3	$45.92	7.667%	$49.4407	$49.44	$49.45	$49.40
Purchase #4	$223.28	9.829%	$245.2262	$245.23	$245.25	$245.20
Purchase #5	$162.66	10.141%	$179.1554	$179.16	$179.15	$179.20
Purchase #6	$58.47	9.750%	$64.1708	$64.17	$64.15	$64.20
Purchase #7	$84.94	6.262%	$90.2589	$90.26	$90.25	$90.30
7 purchase totals =	$920.43		$1,016.1791	$1,016.19	$1,016.20	$1,016.20