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	$24.28	6.206%	$25.7868	$25.79	$25.80	$25.80
Purchase #2	$79.77	11.280%	$88.7681	$88.77	$88.75	$88.80
Purchase #3	$109.34	12.750%	$123.2809	$123.28	$123.30	$123.30
Purchase #4	$191.70	6.491%	$204.1432	$204.14	$204.15	$204.10
Purchase #5	$61.49	6.336%	$65.386	$65.39	$65.40	$65.40
Purchase #6	$199.42	10.118%	$219.5973	$219.60	$219.60	$219.60
Purchase #7	$53.31	11.582%	$59.4844	$59.48	$59.50	$59.50
7 purchase totals =	$719.31		$786.4467	$786.45	$786.50	$786.50