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	$133.42	13.245%	$151.0915	$151.09	$151.10	$151.10
Purchase #2	$37.94	5.779%	$40.1326	$40.13	$40.15	$40.10
Purchase #3	$51.39	10.327%	$56.697	$56.70	$56.70	$56.70
Purchase #4	$59.68	12.598%	$67.1985	$67.20	$67.20	$67.20
Purchase #5	$79.47	8.506%	$86.2297	$86.23	$86.25	$86.20
Purchase #6	$95.67	4.322%	$99.8049	$99.80	$99.80	$99.80
Purchase #7	$242.45	10.695%	$268.38	$268.38	$268.40	$268.40
7 purchase totals =	$700.02		$769.5342	$769.53	$769.60	$769.50