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	$152.69	12.365%	$171.5701	$171.57	$171.55	$171.60
Purchase #2	$10.58	6.147%	$11.2304	$11.23	$11.25	$11.20
Purchase #3	$138.94	10.760%	$153.8899	$153.89	$153.90	$153.90
Purchase #4	$92.80	8.652%	$100.8291	$100.83	$100.85	$100.80
Purchase #5	$197.96	9.217%	$216.206	$216.21	$216.20	$216.20
Purchase #6	$69.72	13.115%	$78.8638	$78.86	$78.85	$78.90
Purchase #7	$159.42	4.597%	$166.7485	$166.75	$166.75	$166.70
7 purchase totals =	$822.11		$899.3378	$899.34	$899.35	$899.30