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	$193.39	6.172%	$205.326	$205.33	$205.35	$205.30
Purchase #2	$141.97	11.304%	$158.0183	$158.02	$158.00	$158.00
Purchase #3	$153.50	9.313%	$167.7955	$167.80	$167.80	$167.80
Purchase #4	$78.89	9.787%	$86.611	$86.61	$86.60	$86.60
Purchase #5	$72.30	7.493%	$77.7174	$77.72	$77.70	$77.70
Purchase #6	$116.83	10.139%	$128.6754	$128.68	$128.70	$128.70
Purchase #7	$185.38	8.238%	$200.6516	$200.65	$200.65	$200.70
7 purchase totals =	$942.26		$1,024.7952	$1,024.81	$1,024.80	$1,024.80