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	$196.79	13.166%	$222.6994	$222.70	$222.70	$222.70
Purchase #2	$69.47	3.805%	$72.1133	$72.11	$72.10	$72.10
Purchase #3	$178.56	7.530%	$192.0056	$192.01	$192.00	$192.00
Purchase #4	$146.59	3.266%	$151.3776	$151.38	$151.40	$151.40
Purchase #5	$247.77	12.258%	$278.1416	$278.14	$278.15	$278.10
Purchase #6	$164.66	13.653%	$187.141	$187.14	$187.15	$187.10
Purchase #7	$26.45	12.680%	$29.8039	$29.80	$29.80	$29.80
7 purchase totals =	$1,030.29		$1,133.2824	$1,133.28	$1,133.30	$1,133.20