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	$250.32	12.869%	$282.5337	$282.53	$282.55	$282.50
Purchase #2	$55.29	3.608%	$57.2849	$57.28	$57.30	$57.30
Purchase #3	$239.49	6.200%	$254.3384	$254.34	$254.35	$254.30
Purchase #4	$230.90	8.440%	$250.388	$250.39	$250.40	$250.40
Purchase #5	$14.34	12.189%	$16.0879	$16.09	$16.10	$16.10
Purchase #6	$130.76	10.828%	$144.9187	$144.92	$144.90	$144.90
Purchase #7	$33.72	11.560%	$37.618	$37.62	$37.60	$37.60
7 purchase totals =	$954.82		$1,043.1696	$1,043.17	$1,043.20	$1,043.10