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	$204.32	6.829%	$218.273	$218.27	$218.25	$218.30
Purchase #2	$111.89	5.789%	$118.3673	$118.37	$118.35	$118.40
Purchase #3	$26.28	11.461%	$29.292	$29.29	$29.30	$29.30
Purchase #4	$141.94	6.394%	$151.0156	$151.02	$151.00	$151.00
Purchase #5	$213.52	6.441%	$227.2728	$227.27	$227.25	$227.30
Purchase #6	$138.90	4.805%	$145.5741	$145.57	$145.55	$145.60
Purchase #7	$103.48	12.823%	$116.7492	$116.75	$116.75	$116.70
7 purchase totals =	$940.33		$1,006.5440	$1,006.54	$1,006.45	$1,006.60