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	$104.69	7.130%	$112.1544	$112.15	$112.15	$112.20
Purchase #2	$164.32	4.218%	$171.251	$171.25	$171.25	$171.30
Purchase #3	$186.83	9.661%	$204.8796	$204.88	$204.90	$204.90
Purchase #4	$146.56	3.447%	$151.6119	$151.61	$151.60	$151.60
Purchase #5	$16.58	9.431%	$18.1437	$18.14	$18.15	$18.10
Purchase #6	$31.29	12.126%	$35.0842	$35.08	$35.10	$35.10
Purchase #7	$74.86	6.187%	$79.4916	$79.49	$79.50	$79.50
7 purchase totals =	$725.13		$772.6164	$772.60	$772.65	$772.70