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	$99.78	11.846%	$111.5999	$111.60	$111.60	$111.60
Purchase #2	$25.45	13.451%	$28.8733	$28.87	$28.85	$28.90
Purchase #3	$179.48	10.447%	$198.2303	$198.23	$198.25	$198.20
Purchase #4	$76.35	3.689%	$79.1666	$79.17	$79.15	$79.20
Purchase #5	$155.90	4.208%	$162.4603	$162.46	$162.45	$162.50
Purchase #6	$246.97	5.588%	$260.7707	$260.77	$260.75	$260.80
Purchase #7	$240.44	10.174%	$264.9024	$264.90	$264.90	$264.90
7 purchase totals =	$1,024.37		$1,106.0035	$1,106.00	$1,105.95	$1,106.10