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	$141.34	12.470%	$158.9651	$158.97	$158.95	$159.00
Purchase #2	$233.82	9.403%	$255.8061	$255.81	$255.80	$255.80
Purchase #3	$172.81	5.837%	$182.8969	$182.90	$182.90	$182.90
Purchase #4	$154.79	7.508%	$166.4116	$166.41	$166.40	$166.40
Purchase #5	$163.39	6.174%	$173.4777	$173.48	$173.50	$173.50
Purchase #6	$94.53	5.671%	$99.8908	$99.89	$99.90	$99.90
Purchase #7	$30.73	5.708%	$32.4841	$32.48	$32.50	$32.50
7 purchase totals =	$991.41		$1,069.9323	$1,069.94	$1,069.95	$1,070.00