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	$102.86	10.584%	$113.7467	$113.75	$113.75	$113.70
Purchase #2	$130.38	11.152%	$144.92	$144.92	$144.90	$144.90
Purchase #3	$98.30	6.136%	$104.3317	$104.33	$104.35	$104.30
Purchase #4	$219.29	3.494%	$226.952	$226.95	$226.95	$227.00
Purchase #5	$178.84	5.210%	$188.1576	$188.16	$188.15	$188.20
Purchase #6	$152.31	8.548%	$165.3295	$165.33	$165.35	$165.30
Purchase #7	$33.79	12.261%	$37.933	$37.93	$37.95	$37.90
7 purchase totals =	$915.77		$981.3705	$981.37	$981.40	$981.30