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	$185.25	12.597%	$208.5859	$208.59	$208.60	$208.60
Purchase #2	$160.83	13.431%	$182.4311	$182.43	$182.45	$182.40
Purchase #3	$205.96	7.314%	$221.0239	$221.02	$221.00	$221.00
Purchase #4	$213.62	12.153%	$239.5812	$239.58	$239.60	$239.60
Purchase #5	$80.98	3.503%	$83.8167	$83.82	$83.80	$83.80
Purchase #6	$192.82	12.629%	$217.1712	$217.17	$217.15	$217.20
Purchase #7	$11.72	9.743%	$12.8619	$12.86	$12.85	$12.90
7 purchase totals =	$1,051.18		$1,165.4719	$1,165.47	$1,165.45	$1,165.50