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	$22.56	5.700%	$23.8459	$23.85	$23.85	$23.80
Purchase #2	$155.60	5.597%	$164.3089	$164.31	$164.30	$164.30
Purchase #3	$188.37	4.188%	$196.2589	$196.26	$196.25	$196.30
Purchase #4	$89.40	13.106%	$101.1168	$101.12	$101.10	$101.10
Purchase #5	$106.47	3.246%	$109.926	$109.93	$109.95	$109.90
Purchase #6	$85.28	9.775%	$93.6161	$93.62	$93.60	$93.60
Purchase #7	$244.32	9.525%	$267.5915	$267.59	$267.60	$267.60
7 purchase totals =	$892.00		$956.6641	$956.68	$956.65	$956.60