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	$152.86	6.285%	$162.4673	$162.47	$162.45	$162.50
Purchase #2	$70.69	10.574%	$78.1648	$78.16	$78.15	$78.20
Purchase #3	$101.75	7.684%	$109.5685	$109.57	$109.55	$109.60
Purchase #4	$138.97	9.747%	$152.5154	$152.52	$152.50	$152.50
Purchase #5	$29.56	12.374%	$33.2178	$33.22	$33.20	$33.20
Purchase #6	$118.44	5.503%	$124.9578	$124.96	$124.95	$125.00
Purchase #7	$244.52	11.486%	$272.6056	$272.61	$272.60	$272.60
7 purchase totals =	$856.79		$933.4972	$933.51	$933.40	$933.60