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	$49.59	7.649%	$53.3831	$53.38	$53.40	$53.40
Purchase #2	$66.70	5.772%	$70.5499	$70.55	$70.55	$70.50
Purchase #3	$194.88	7.355%	$209.2134	$209.21	$209.20	$209.20
Purchase #4	$163.28	10.806%	$180.924	$180.92	$180.90	$180.90
Purchase #5	$144.61	7.388%	$155.2938	$155.29	$155.30	$155.30
Purchase #6	$133.27	13.152%	$150.7977	$150.80	$150.80	$150.80
Purchase #7	$245.68	8.390%	$266.2926	$266.29	$266.30	$266.30
7 purchase totals =	$998.01		$1,086.4545	$1,086.44	$1,086.45	$1,086.40