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	$228.65	10.751%	$253.2322	$253.23	$253.25	$253.20
Purchase #2	$214.69	9.868%	$235.8756	$235.88	$235.90	$235.90
Purchase #3	$216.32	10.755%	$239.5852	$239.59	$239.60	$239.60
Purchase #4	$88.62	12.239%	$99.4662	$99.47	$99.45	$99.50
Purchase #5	$12.96	11.481%	$14.4479	$14.45	$14.45	$14.40
Purchase #6	$53.79	10.366%	$59.3659	$59.37	$59.35	$59.40
Purchase #7	$46.49	11.692%	$51.9256	$51.93	$51.95	$51.90
7 purchase totals =	$861.52		$953.8986	$953.92	$953.95	$953.90