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	$88.94	6.867%	$95.0475	$95.05	$95.05	$95.00
Purchase #2	$182.90	4.760%	$191.606	$191.61	$191.60	$191.60
Purchase #3	$11.32	7.404%	$12.1581	$12.16	$12.15	$12.20
Purchase #4	$230.92	13.252%	$261.5215	$261.52	$261.50	$261.50
Purchase #5	$145.59	6.483%	$155.0286	$155.03	$155.05	$155.00
Purchase #6	$35.93	4.337%	$37.4883	$37.49	$37.50	$37.50
Purchase #7	$51.46	6.257%	$54.6799	$54.68	$54.70	$54.70
7 purchase totals =	$747.06		$807.5299	$807.54	$807.55	$807.50