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	$107.25	4.691%	$112.2811	$112.28	$112.30	$112.30
Purchase #2	$12.31	3.577%	$12.7503	$12.75	$12.75	$12.80
Purchase #3	$63.85	4.629%	$66.8056	$66.81	$66.80	$66.80
Purchase #4	$31.40	13.769%	$35.7235	$35.72	$35.70	$35.70
Purchase #5	$34.46	8.573%	$37.4143	$37.41	$37.40	$37.40
Purchase #6	$99.26	5.147%	$104.3689	$104.37	$104.35	$104.40
Purchase #7	$166.52	8.385%	$180.4827	$180.48	$180.50	$180.50
7 purchase totals =	$515.05		$549.8264	$549.82	$549.80	$549.90