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	$160.75	11.799%	$179.7169	$179.72	$179.70	$179.70
Purchase #2	$192.26	8.852%	$209.2789	$209.28	$209.30	$209.30
Purchase #3	$204.48	7.514%	$219.8446	$219.84	$219.85	$219.80
Purchase #4	$96.35	9.466%	$105.4705	$105.47	$105.45	$105.50
Purchase #5	$171.94	12.813%	$193.9707	$193.97	$193.95	$194.00
Purchase #6	$38.75	10.531%	$42.8308	$42.83	$42.85	$42.80
Purchase #7	$59.83	13.508%	$67.9118	$67.91	$67.90	$67.90
7 purchase totals =	$924.36		$1,019.0242	$1,019.02	$1,019.00	$1,019.00