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	$62.60	11.406%	$69.7402	$69.74	$69.75	$69.70
Purchase #2	$228.53	6.280%	$242.8817	$242.88	$242.90	$242.90
Purchase #3	$34.39	10.609%	$38.0384	$38.04	$38.05	$38.00
Purchase #4	$225.86	13.116%	$255.4838	$255.48	$255.50	$255.50
Purchase #5	$114.81	10.786%	$127.1934	$127.19	$127.20	$127.20
Purchase #6	$19.35	5.675%	$20.4481	$20.45	$20.45	$20.40
Purchase #7	$58.42	5.588%	$61.6845	$61.68	$61.70	$61.70
7 purchase totals =	$743.96		$815.4701	$815.46	$815.55	$815.40