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	$158.93	13.779%	$180.829	$180.83	$180.85	$180.80
Purchase #2	$237.41	6.628%	$253.1455	$253.15	$253.15	$253.10
Purchase #3	$65.80	4.266%	$68.607	$68.61	$68.60	$68.60
Purchase #4	$142.50	12.547%	$160.3795	$160.38	$160.40	$160.40
Purchase #5	$143.26	6.700%	$152.8584	$152.86	$152.85	$152.90
Purchase #6	$67.45	7.261%	$72.3475	$72.35	$72.35	$72.30
Purchase #7	$117.69	9.849%	$129.2813	$129.28	$129.30	$129.30
7 purchase totals =	$933.04		$1,017.4482	$1,017.46	$1,017.50	$1,017.40