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	$102.56	7.513%	$110.2653	$110.27	$110.25	$110.30
Purchase #2	$59.36	5.103%	$62.3891	$62.39	$62.40	$62.40
Purchase #3	$81.62	13.226%	$92.4151	$92.42	$92.40	$92.40
Purchase #4	$249.82	11.570%	$278.7242	$278.72	$278.70	$278.70
Purchase #5	$157.96	10.526%	$174.5869	$174.59	$174.60	$174.60
Purchase #6	$249.65	5.197%	$262.6243	$262.62	$262.60	$262.60
Purchase #7	$57.88	3.160%	$59.709	$59.71	$59.70	$59.70
7 purchase totals =	$958.85		$1,040.7139	$1,040.72	$1,040.65	$1,040.70