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	$133.27	13.219%	$150.887	$150.89	$150.90	$150.90
Purchase #2	$48.79	5.816%	$51.6276	$51.63	$51.65	$51.60
Purchase #3	$77.31	4.235%	$80.5841	$80.58	$80.60	$80.60
Purchase #4	$214.89	5.786%	$227.3235	$227.32	$227.30	$227.30
Purchase #5	$243.54	4.763%	$255.1398	$255.14	$255.15	$255.10
Purchase #6	$182.89	12.209%	$205.219	$205.22	$205.20	$205.20
Purchase #7	$99.82	3.247%	$103.0612	$103.06	$103.05	$103.10
7 purchase totals =	$1,000.51		$1,073.8422	$1,073.84	$1,073.85	$1,073.80