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	$232.44	9.132%	$253.6664	$253.67	$253.65	$253.70
Purchase #2	$198.41	10.339%	$218.9236	$218.92	$218.90	$218.90
Purchase #3	$180.71	5.268%	$190.2298	$190.23	$190.25	$190.20
Purchase #4	$111.88	13.743%	$127.2557	$127.26	$127.25	$127.30
Purchase #5	$178.74	9.411%	$195.5612	$195.56	$195.55	$195.60
Purchase #6	$177.31	8.522%	$192.4204	$192.42	$192.40	$192.40
Purchase #7	$71.65	9.413%	$78.3944	$78.39	$78.40	$78.40
7 purchase totals =	$1,151.14		$1,256.4515	$1,256.45	$1,256.40	$1,256.50