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	$150.88	5.195%	$158.7182	$158.72	$158.70	$158.70
Purchase #2	$18.25	6.425%	$19.4226	$19.42	$19.40	$19.40
Purchase #3	$117.71	4.762%	$123.3154	$123.32	$123.30	$123.30
Purchase #4	$198.61	9.540%	$217.5574	$217.56	$217.55	$217.60
Purchase #5	$172.79	6.671%	$184.3168	$184.32	$184.30	$184.30
Purchase #6	$151.72	11.221%	$168.7445	$168.74	$168.75	$168.70
Purchase #7	$65.56	8.365%	$71.0441	$71.04	$71.05	$71.00
7 purchase totals =	$875.52		$943.1190	$943.12	$943.05	$943.00