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	$95.60	4.550%	$99.9498	$99.95	$99.95	$99.90
Purchase #2	$240.42	13.647%	$273.2301	$273.23	$273.25	$273.20
Purchase #3	$204.89	3.536%	$212.1349	$212.13	$212.15	$212.10
Purchase #4	$96.48	8.391%	$104.5756	$104.58	$104.60	$104.60
Purchase #5	$185.86	5.334%	$195.7738	$195.77	$195.75	$195.80
Purchase #6	$118.32	12.447%	$133.0473	$133.05	$133.05	$133.00
Purchase #7	$74.62	5.693%	$78.8681	$78.87	$78.85	$78.90
7 purchase totals =	$1,016.19		$1,097.5796	$1,097.58	$1,097.60	$1,097.50