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	$49.86	7.264%	$53.4818	$53.48	$53.50	$53.50
Purchase #2	$171.50	4.148%	$178.6138	$178.61	$178.60	$178.60
Purchase #3	$144.91	9.532%	$158.7228	$158.72	$158.70	$158.70
Purchase #4	$148.94	6.365%	$158.42	$158.42	$158.40	$158.40
Purchase #5	$73.96	6.256%	$78.5869	$78.59	$78.60	$78.60
Purchase #6	$44.43	5.545%	$46.8936	$46.89	$46.90	$46.90
Purchase #7	$102.41	10.631%	$113.2972	$113.30	$113.30	$113.30
7 purchase totals =	$736.01		$788.0161	$788.01	$788.00	$788.00