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	$199.56	11.545%	$222.5992	$222.60	$222.60	$222.60
Purchase #2	$67.31	3.117%	$69.4081	$69.41	$69.40	$69.40
Purchase #3	$250.95	10.798%	$278.0476	$278.05	$278.05	$278.00
Purchase #4	$250.35	11.286%	$278.6045	$278.60	$278.60	$278.60
Purchase #5	$130.88	11.452%	$145.8684	$145.87	$145.85	$145.90
Purchase #6	$173.98	13.142%	$196.8445	$196.84	$196.85	$196.80
Purchase #7	$162.86	7.229%	$174.6331	$174.63	$174.65	$174.60
7 purchase totals =	$1,235.89		$1,366.0054	$1,366.00	$1,366.00	$1,365.90