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	$116.57	5.617%	$123.1177	$123.12	$123.10	$123.10
Purchase #2	$176.56	3.246%	$182.2911	$182.29	$182.30	$182.30
Purchase #3	$14.26	7.713%	$15.3599	$15.36	$15.35	$15.40
Purchase #4	$155.58	7.733%	$167.611	$167.61	$167.60	$167.60
Purchase #5	$45.49	12.336%	$51.1016	$51.10	$51.10	$51.10
Purchase #6	$133.63	5.670%	$141.2068	$141.21	$141.20	$141.20
Purchase #7	$146.93	12.728%	$165.6313	$165.63	$165.65	$165.60
7 purchase totals =	$789.02		$846.3194	$846.32	$846.30	$846.30