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	$138.81	8.727%	$150.9239	$150.92	$150.90	$150.90
Purchase #2	$68.36	4.443%	$71.3972	$71.40	$71.40	$71.40
Purchase #3	$175.88	9.640%	$192.8348	$192.83	$192.85	$192.80
Purchase #4	$140.90	12.578%	$158.6224	$158.62	$158.60	$158.60
Purchase #5	$188.91	3.775%	$196.0414	$196.04	$196.05	$196.00
Purchase #6	$187.45	11.530%	$209.063	$209.06	$209.05	$209.10
Purchase #7	$108.52	4.587%	$113.4978	$113.50	$113.50	$113.50
7 purchase totals =	$1,008.83		$1,092.3805	$1,092.37	$1,092.35	$1,092.30