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	$93.35	13.355%	$105.8169	$105.82	$105.80	$105.80
Purchase #2	$160.36	12.606%	$180.575	$180.58	$180.60	$180.60
Purchase #3	$213.75	4.266%	$222.8686	$222.87	$222.85	$222.90
Purchase #4	$69.79	13.281%	$79.0588	$79.06	$79.05	$79.10
Purchase #5	$217.31	11.740%	$242.8222	$242.82	$242.80	$242.80
Purchase #6	$207.53	5.605%	$219.1621	$219.16	$219.15	$219.20
Purchase #7	$186.77	10.116%	$205.6637	$205.66	$205.65	$205.70
7 purchase totals =	$1,148.86		$1,255.9673	$1,255.97	$1,255.90	$1,256.10