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	$49.81	7.153%	$53.3729	$53.37	$53.35	$53.40
Purchase #2	$248.81	5.564%	$262.6538	$262.65	$262.65	$262.70
Purchase #3	$49.92	6.592%	$53.2107	$53.21	$53.20	$53.20
Purchase #4	$85.36	11.680%	$95.33	$95.33	$95.35	$95.30
Purchase #5	$39.28	8.506%	$42.6212	$42.62	$42.60	$42.60
Purchase #6	$132.62	10.776%	$146.9111	$146.91	$146.90	$146.90
Purchase #7	$88.69	13.351%	$100.531	$100.53	$100.55	$100.50
7 purchase totals =	$694.49		$754.6307	$754.62	$754.60	$754.60