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	$88.36	12.705%	$99.5861	$99.59	$99.60	$99.60
Purchase #2	$172.37	7.242%	$184.853	$184.85	$184.85	$184.90
Purchase #3	$150.82	4.315%	$157.3279	$157.33	$157.35	$157.30
Purchase #4	$219.90	5.485%	$231.9615	$231.96	$231.95	$232.00
Purchase #5	$245.66	9.531%	$269.0739	$269.07	$269.05	$269.10
Purchase #6	$150.86	4.819%	$158.1299	$158.13	$158.15	$158.10
Purchase #7	$51.38	3.858%	$53.3622	$53.36	$53.35	$53.40
7 purchase totals =	$1,079.35		$1,154.2945	$1,154.29	$1,154.30	$1,154.40