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	$216.79	4.464%	$226.4675	$226.47	$226.45	$226.50
Purchase #2	$203.96	6.519%	$217.2562	$217.26	$217.25	$217.30
Purchase #3	$73.94	5.797%	$78.2263	$78.23	$78.25	$78.20
Purchase #4	$167.52	3.540%	$173.4502	$173.45	$173.45	$173.50
Purchase #5	$238.62	10.810%	$264.4148	$264.41	$264.40	$264.40
Purchase #6	$108.89	13.319%	$123.3931	$123.39	$123.40	$123.40
Purchase #7	$141.73	8.722%	$154.0917	$154.09	$154.10	$154.10
7 purchase totals =	$1,151.45		$1,237.2998	$1,237.30	$1,237.30	$1,237.40