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	$103.99	5.565%	$109.777	$109.78	$109.80	$109.80
Purchase #2	$10.89	13.135%	$12.3204	$12.32	$12.30	$12.30
Purchase #3	$92.44	6.327%	$98.2887	$98.29	$98.30	$98.30
Purchase #4	$30.26	13.368%	$34.3052	$34.31	$34.30	$34.30
Purchase #5	$47.42	8.860%	$51.6214	$51.62	$51.60	$51.60
Purchase #6	$154.38	10.492%	$170.5775	$170.58	$170.60	$170.60
Purchase #7	$189.41	3.751%	$196.5148	$196.51	$196.50	$196.50
7 purchase totals =	$628.79		$673.4050	$673.41	$673.40	$673.40