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	$102.30	9.733%	$112.2569	$112.26	$112.25	$112.30
Purchase #2	$167.36	7.542%	$179.9823	$179.98	$180.00	$180.00
Purchase #3	$12.28	4.472%	$12.8292	$12.83	$12.85	$12.80
Purchase #4	$38.79	10.436%	$42.8381	$42.84	$42.85	$42.80
Purchase #5	$207.25	9.451%	$226.8372	$226.84	$226.85	$226.80
Purchase #6	$176.59	6.466%	$188.0083	$188.01	$188.00	$188.00
Purchase #7	$239.29	6.747%	$255.4349	$255.43	$255.45	$255.40
7 purchase totals =	$943.86		$1,018.1869	$1,018.19	$1,018.25	$1,018.10