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	$200.39	13.804%	$228.0518	$228.05	$228.05	$228.10
Purchase #2	$201.45	4.322%	$210.1567	$210.16	$210.15	$210.20
Purchase #3	$153.60	13.852%	$174.8767	$174.88	$174.90	$174.90
Purchase #4	$156.32	7.162%	$167.5156	$167.52	$167.50	$167.50
Purchase #5	$86.45	4.194%	$90.0757	$90.08	$90.10	$90.10
Purchase #6	$231.28	13.748%	$263.0764	$263.08	$263.10	$263.10
Purchase #7	$244.30	8.564%	$265.2219	$265.22	$265.20	$265.20
7 purchase totals =	$1,273.79		$1,398.9748	$1,398.99	$1,399.00	$1,399.10