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	$147.40	5.463%	$155.4525	$155.45	$155.45	$155.50
Purchase #2	$19.97	12.810%	$22.5282	$22.53	$22.55	$22.50
Purchase #3	$141.31	7.276%	$151.5917	$151.59	$151.60	$151.60
Purchase #4	$100.86	12.453%	$113.4201	$113.42	$113.40	$113.40
Purchase #5	$97.79	7.765%	$105.3834	$105.38	$105.40	$105.40
Purchase #6	$120.69	7.476%	$129.7128	$129.71	$129.70	$129.70
Purchase #7	$100.62	7.733%	$108.4009	$108.40	$108.40	$108.40
7 purchase totals =	$728.64		$786.4896	$786.48	$786.50	$786.50