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	$90.81	13.254%	$102.846	$102.85	$102.85	$102.80
Purchase #2	$132.33	4.470%	$138.2452	$138.25	$138.25	$138.20
Purchase #3	$139.95	11.197%	$155.6202	$155.62	$155.60	$155.60
Purchase #4	$199.65	6.474%	$212.5753	$212.58	$212.60	$212.60
Purchase #5	$212.56	13.761%	$241.8104	$241.81	$241.80	$241.80
Purchase #6	$198.83	6.820%	$212.3902	$212.39	$212.40	$212.40
Purchase #7	$98.48	13.150%	$111.4301	$111.43	$111.45	$111.40
7 purchase totals =	$1,072.61		$1,174.9174	$1,174.93	$1,174.95	$1,174.80