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	$144.64	8.857%	$157.4508	$157.45	$157.45	$157.50
Purchase #2	$37.72	3.839%	$39.1681	$39.17	$39.15	$39.20
Purchase #3	$41.88	9.355%	$45.7979	$45.80	$45.80	$45.80
Purchase #4	$98.66	13.110%	$111.5943	$111.59	$111.60	$111.60
Purchase #5	$173.79	8.813%	$189.1061	$189.11	$189.10	$189.10
Purchase #6	$19.32	6.527%	$20.581	$20.58	$20.60	$20.60
Purchase #7	$69.87	3.475%	$72.298	$72.30	$72.30	$72.30
7 purchase totals =	$585.88		$635.9962	$636.00	$636.00	$636.10