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	$71.72	7.423%	$77.0438	$77.04	$77.05	$77.00
Purchase #2	$66.95	6.807%	$71.5073	$71.51	$71.50	$71.50
Purchase #3	$16.91	13.674%	$19.2223	$19.22	$19.20	$19.20
Purchase #4	$244.91	4.371%	$255.615	$255.62	$255.60	$255.60
Purchase #5	$149.61	11.481%	$166.7867	$166.79	$166.80	$166.80
Purchase #6	$95.29	13.665%	$108.3114	$108.31	$108.30	$108.30
Purchase #7	$179.85	6.178%	$190.9611	$190.96	$190.95	$191.00
7 purchase totals =	$825.24		$889.4476	$889.45	$889.40	$889.40