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	$132.61	5.317%	$139.6609	$139.66	$139.65	$139.70
Purchase #2	$180.51	6.514%	$192.2684	$192.27	$192.25	$192.30
Purchase #3	$117.35	10.253%	$129.3819	$129.38	$129.40	$129.40
Purchase #4	$142.74	10.816%	$158.1788	$158.18	$158.20	$158.20
Purchase #5	$162.89	13.539%	$184.9437	$184.94	$184.95	$184.90
Purchase #6	$148.42	12.634%	$167.1714	$167.17	$167.15	$167.20
Purchase #7	$202.38	5.713%	$213.942	$213.94	$213.95	$213.90
7 purchase totals =	$1,086.90		$1,185.5471	$1,185.54	$1,185.55	$1,185.60