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	$57.92	12.645%	$65.244	$65.24	$65.25	$65.20
Purchase #2	$99.37	4.275%	$103.6181	$103.62	$103.60	$103.60
Purchase #3	$176.28	8.126%	$190.6045	$190.60	$190.60	$190.60
Purchase #4	$48.44	8.416%	$52.5167	$52.52	$52.50	$52.50
Purchase #5	$163.71	9.409%	$179.1135	$179.11	$179.10	$179.10
Purchase #6	$244.36	7.409%	$262.4646	$262.46	$262.45	$262.50
Purchase #7	$59.36	5.571%	$62.6669	$62.67	$62.65	$62.70
7 purchase totals =	$849.44		$916.2283	$916.22	$916.15	$916.20