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	$64.89	11.573%	$72.3997	$72.40	$72.40	$72.40
Purchase #2	$200.43	9.588%	$219.6472	$219.65	$219.65	$219.60
Purchase #3	$204.38	6.389%	$217.4378	$217.44	$217.45	$217.40
Purchase #4	$39.29	11.425%	$43.7789	$43.78	$43.80	$43.80
Purchase #5	$83.81	13.381%	$95.0246	$95.02	$95.00	$95.00
Purchase #6	$139.42	3.835%	$144.7668	$144.77	$144.75	$144.80
Purchase #7	$204.69	12.650%	$230.5833	$230.58	$230.60	$230.60
7 purchase totals =	$936.91		$1,023.6383	$1,023.64	$1,023.65	$1,023.60