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	$108.50	3.285%	$112.0642	$112.06	$112.05	$112.10
Purchase #2	$89.73	11.758%	$100.2805	$100.28	$100.30	$100.30
Purchase #3	$31.34	13.580%	$35.596	$35.60	$35.60	$35.60
Purchase #4	$151.72	9.573%	$166.2442	$166.24	$166.25	$166.20
Purchase #5	$77.51	12.134%	$86.9151	$86.92	$86.90	$86.90
Purchase #6	$167.61	9.179%	$182.9949	$182.99	$183.00	$183.00
Purchase #7	$13.62	8.481%	$14.7751	$14.78	$14.80	$14.80
7 purchase totals =	$640.03		$698.8700	$698.87	$698.90	$698.90