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	$18.32	6.681%	$19.544	$19.54	$19.55	$19.50
Purchase #2	$68.28	5.321%	$71.9132	$71.91	$71.90	$71.90
Purchase #3	$82.51	10.553%	$91.2173	$91.22	$91.20	$91.20
Purchase #4	$198.99	7.159%	$213.2357	$213.24	$213.25	$213.20
Purchase #5	$207.35	8.719%	$225.4288	$225.43	$225.45	$225.40
Purchase #6	$112.41	13.175%	$127.22	$127.22	$127.20	$127.20
Purchase #7	$229.40	12.783%	$258.7242	$258.72	$258.70	$258.70
7 purchase totals =	$917.26		$1,007.2832	$1,007.28	$1,007.25	$1,007.10