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	$12.96	11.160%	$14.4063	$14.41	$14.40	$14.40
Purchase #2	$165.80	11.723%	$185.2367	$185.24	$185.25	$185.20
Purchase #3	$33.76	12.511%	$37.9837	$37.98	$38.00	$38.00
Purchase #4	$25.26	6.212%	$26.8292	$26.83	$26.85	$26.80
Purchase #5	$14.31	7.394%	$15.3681	$15.37	$15.35	$15.40
Purchase #6	$123.60	3.772%	$128.2622	$128.26	$128.25	$128.30
Purchase #7	$107.84	3.162%	$111.2499	$111.25	$111.25	$111.20
7 purchase totals =	$483.53		$519.3361	$519.34	$519.35	$519.30