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	$28.85	3.803%	$29.9472	$29.95	$29.95	$29.90
Purchase #2	$158.86	13.370%	$180.0996	$180.10	$180.10	$180.10
Purchase #3	$33.75	9.842%	$37.0717	$37.07	$37.05	$37.10
Purchase #4	$228.60	11.728%	$255.4102	$255.41	$255.40	$255.40
Purchase #5	$81.80	7.602%	$88.0184	$88.02	$88.00	$88.00
Purchase #6	$227.88	13.663%	$259.0152	$259.02	$259.00	$259.00
Purchase #7	$156.35	8.435%	$169.5381	$169.54	$169.55	$169.50
7 purchase totals =	$916.09		$1,019.1004	$1,019.11	$1,019.05	$1,019.00