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	$150.46	11.426%	$167.6516	$167.65	$167.65	$167.70
Purchase #2	$179.75	3.274%	$185.635	$185.64	$185.65	$185.60
Purchase #3	$51.89	11.592%	$57.9051	$57.91	$57.90	$57.90
Purchase #4	$128.39	13.742%	$146.0334	$146.03	$146.05	$146.00
Purchase #5	$138.84	13.732%	$157.9055	$157.91	$157.90	$157.90
Purchase #6	$84.94	8.158%	$91.8694	$91.87	$91.85	$91.90
Purchase #7	$247.45	7.808%	$266.7709	$266.77	$266.75	$266.80
7 purchase totals =	$981.72		$1,073.7709	$1,073.78	$1,073.75	$1,073.80