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	$95.52	4.531%	$99.848	$99.85	$99.85	$99.80
Purchase #2	$53.44	10.797%	$59.2099	$59.21	$59.20	$59.20
Purchase #3	$102.58	4.749%	$107.4515	$107.45	$107.45	$107.50
Purchase #4	$203.42	3.824%	$211.1988	$211.20	$211.20	$211.20
Purchase #5	$168.70	8.169%	$182.4811	$182.48	$182.50	$182.50
Purchase #6	$184.80	11.253%	$205.5955	$205.60	$205.60	$205.60
Purchase #7	$105.48	5.288%	$111.0578	$111.06	$111.05	$111.10
7 purchase totals =	$913.94		$976.8426	$976.85	$976.85	$976.90