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	$133.82	13.125%	$151.3839	$151.38	$151.40	$151.40
Purchase #2	$219.41	10.674%	$242.8298	$242.83	$242.85	$242.80
Purchase #3	$40.78	5.356%	$42.9642	$42.96	$42.95	$43.00
Purchase #4	$173.32	3.231%	$178.92	$178.92	$178.90	$178.90
Purchase #5	$235.80	5.359%	$248.4365	$248.44	$248.45	$248.40
Purchase #6	$92.77	8.607%	$100.7547	$100.75	$100.75	$100.80
Purchase #7	$95.75	6.823%	$102.283	$102.28	$102.30	$102.30
7 purchase totals =	$991.65		$1,067.5721	$1,067.56	$1,067.60	$1,067.60