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	$112.65	4.717%	$117.9637	$117.96	$117.95	$118.00
Purchase #2	$134.80	3.287%	$139.2309	$139.23	$139.25	$139.20
Purchase #3	$50.41	6.420%	$53.6463	$53.65	$53.65	$53.60
Purchase #4	$142.89	13.499%	$162.1787	$162.18	$162.20	$162.20
Purchase #5	$83.60	8.312%	$90.5488	$90.55	$90.55	$90.50
Purchase #6	$60.69	4.459%	$63.3962	$63.40	$63.40	$63.40
Purchase #7	$133.47	9.183%	$145.7266	$145.73	$145.75	$145.70
7 purchase totals =	$718.51		$772.6912	$772.70	$772.75	$772.60