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	$213.28	3.412%	$220.5571	$220.56	$220.55	$220.60
Purchase #2	$65.40	11.109%	$72.6653	$72.67	$72.65	$72.70
Purchase #3	$10.35	5.108%	$10.8787	$10.88	$10.90	$10.90
Purchase #4	$77.94	13.205%	$88.232	$88.23	$88.25	$88.20
Purchase #5	$130.77	13.206%	$148.0395	$148.04	$148.05	$148.00
Purchase #6	$139.80	10.750%	$154.8285	$154.83	$154.85	$154.80
Purchase #7	$35.97	4.618%	$37.6311	$37.63	$37.65	$37.60
7 purchase totals =	$673.51		$732.8322	$732.84	$732.90	$732.80