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	$92.32	13.657%	$104.9281	$104.93	$104.95	$104.90
Purchase #2	$13.31	12.720%	$15.003	$15.00	$15.00	$15.00
Purchase #3	$100.64	10.770%	$111.4789	$111.48	$111.50	$111.50
Purchase #4	$99.78	9.490%	$109.2491	$109.25	$109.25	$109.20
Purchase #5	$20.94	5.359%	$22.0622	$22.06	$22.05	$22.10
Purchase #6	$82.30	13.764%	$93.6278	$93.63	$93.65	$93.60
Purchase #7	$125.97	7.642%	$135.5966	$135.60	$135.60	$135.60
7 purchase totals =	$535.26		$591.9457	$591.95	$592.00	$591.90