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	$170.33	9.706%	$186.8622	$186.86	$186.85	$186.90
Purchase #2	$92.86	8.170%	$100.4467	$100.45	$100.45	$100.40
Purchase #3	$162.56	13.648%	$184.7462	$184.75	$184.75	$184.70
Purchase #4	$17.25	13.468%	$19.5732	$19.57	$19.55	$19.60
Purchase #5	$10.62	11.827%	$11.876	$11.88	$11.90	$11.90
Purchase #6	$158.44	9.454%	$173.4189	$173.42	$173.40	$173.40
Purchase #7	$16.33	13.536%	$18.5404	$18.54	$18.55	$18.50
7 purchase totals =	$628.39		$695.4636	$695.47	$695.45	$695.40