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	$113.31	7.324%	$121.6088	$121.61	$121.60	$121.60
Purchase #2	$21.66	3.170%	$22.3466	$22.35	$22.35	$22.30
Purchase #3	$126.92	4.129%	$132.1605	$132.16	$132.15	$132.20
Purchase #4	$38.48	3.578%	$39.8568	$39.86	$39.85	$39.90
Purchase #5	$172.78	13.623%	$196.3178	$196.32	$196.30	$196.30
Purchase #6	$55.59	6.226%	$59.051	$59.05	$59.05	$59.10
Purchase #7	$192.55	3.142%	$198.5999	$198.60	$198.60	$198.60
7 purchase totals =	$721.29		$769.9414	$769.95	$769.90	$770.00