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	$116.76	13.275%	$132.2599	$132.26	$132.25	$132.30
Purchase #2	$159.44	6.127%	$169.2089	$169.21	$169.20	$169.20
Purchase #3	$120.93	13.768%	$137.5796	$137.58	$137.60	$137.60
Purchase #4	$119.83	9.476%	$131.1851	$131.19	$131.20	$131.20
Purchase #5	$113.29	4.556%	$118.4515	$118.45	$118.45	$118.50
Purchase #6	$243.63	3.198%	$251.4213	$251.42	$251.40	$251.40
Purchase #7	$116.62	3.699%	$120.9338	$120.93	$120.95	$120.90
7 purchase totals =	$990.50		$1,061.0401	$1,061.04	$1,061.05	$1,061.10