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	$50.59	6.772%	$54.016	$54.02	$54.00	$54.00
Purchase #2	$70.30	11.860%	$78.6376	$78.64	$78.65	$78.60
Purchase #3	$238.89	12.800%	$269.4679	$269.47	$269.45	$269.50
Purchase #4	$42.51	6.273%	$45.1767	$45.18	$45.20	$45.20
Purchase #5	$140.34	8.379%	$152.0991	$152.10	$152.10	$152.10
Purchase #6	$42.54	9.623%	$46.6336	$46.63	$46.65	$46.60
Purchase #7	$201.86	12.830%	$227.7586	$227.76	$227.75	$227.80
7 purchase totals =	$787.03		$873.7895	$873.80	$873.80	$873.80