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	$99.79	3.723%	$103.5052	$103.51	$103.50	$103.50
Purchase #2	$180.67	8.643%	$196.2853	$196.29	$196.30	$196.30
Purchase #3	$232.88	3.683%	$241.457	$241.46	$241.45	$241.50
Purchase #4	$138.60	12.322%	$155.6783	$155.68	$155.70	$155.70
Purchase #5	$23.56	11.825%	$26.346	$26.35	$26.35	$26.30
Purchase #6	$102.64	13.347%	$116.3394	$116.34	$116.35	$116.30
Purchase #7	$181.32	4.195%	$188.9264	$188.93	$188.95	$188.90
7 purchase totals =	$959.46		$1,028.5376	$1,028.56	$1,028.60	$1,028.50