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	$67.96	8.560%	$73.7774	$73.78	$73.80	$73.80
Purchase #2	$166.56	9.126%	$181.7603	$181.76	$181.75	$181.80
Purchase #3	$68.94	11.521%	$76.8826	$76.88	$76.90	$76.90
Purchase #4	$64.72	10.463%	$71.4917	$71.49	$71.50	$71.50
Purchase #5	$10.71	7.181%	$11.4791	$11.48	$11.50	$11.50
Purchase #6	$107.55	3.746%	$111.5788	$111.58	$111.60	$111.60
Purchase #7	$27.64	10.326%	$30.4941	$30.49	$30.50	$30.50
7 purchase totals =	$514.08		$557.4640	$557.46	$557.55	$557.60