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	$166.75	5.323%	$175.6261	$175.63	$175.65	$175.60
Purchase #2	$78.45	11.676%	$87.6098	$87.61	$87.60	$87.60
Purchase #3	$182.61	9.226%	$199.4576	$199.46	$199.45	$199.50
Purchase #4	$233.51	6.367%	$248.3776	$248.38	$248.40	$248.40
Purchase #5	$92.60	7.396%	$99.4487	$99.45	$99.45	$99.40
Purchase #6	$103.57	13.403%	$117.4515	$117.45	$117.45	$117.50
Purchase #7	$50.78	7.304%	$54.489	$54.49	$54.50	$54.50
7 purchase totals =	$908.27		$982.4603	$982.47	$982.50	$982.50