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	$52.26	3.282%	$53.9752	$53.98	$54.00	$54.00
Purchase #2	$115.51	13.572%	$131.187	$131.19	$131.20	$131.20
Purchase #3	$213.94	5.491%	$225.6874	$225.69	$225.70	$225.70
Purchase #4	$58.38	3.449%	$60.3935	$60.39	$60.40	$60.40
Purchase #5	$95.66	10.475%	$105.6804	$105.68	$105.70	$105.70
Purchase #6	$162.32	3.813%	$168.5093	$168.51	$168.50	$168.50
Purchase #7	$39.54	9.769%	$43.4027	$43.40	$43.40	$43.40
7 purchase totals =	$737.61		$788.8355	$788.84	$788.90	$788.90