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	$62.56	8.491%	$67.872	$67.87	$67.85	$67.90
Purchase #2	$125.56	11.508%	$140.0094	$140.01	$140.00	$140.00
Purchase #3	$162.79	3.737%	$168.8735	$168.87	$168.85	$168.90
Purchase #4	$199.86	7.422%	$214.6936	$214.69	$214.70	$214.70
Purchase #5	$146.95	11.836%	$164.343	$164.34	$164.35	$164.30
Purchase #6	$46.31	3.407%	$47.8878	$47.89	$47.90	$47.90
Purchase #7	$64.70	8.421%	$70.1484	$70.15	$70.15	$70.10
7 purchase totals =	$808.73		$873.8277	$873.82	$873.80	$873.80