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	$180.43	4.720%	$188.9463	$188.95	$188.95	$188.90
Purchase #2	$118.96	7.178%	$127.4989	$127.50	$127.50	$127.50
Purchase #3	$16.64	11.554%	$18.5626	$18.56	$18.55	$18.60
Purchase #4	$61.96	5.413%	$65.3139	$65.31	$65.30	$65.30
Purchase #5	$218.83	11.225%	$243.3937	$243.39	$243.40	$243.40
Purchase #6	$205.56	11.527%	$229.2549	$229.25	$229.25	$229.30
Purchase #7	$208.91	4.182%	$217.6466	$217.65	$217.65	$217.60
7 purchase totals =	$1,011.29		$1,090.6169	$1,090.61	$1,090.60	$1,090.60