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	$141.85	9.375%	$155.1484	$155.15	$155.15	$155.10
Purchase #2	$100.77	9.431%	$110.2736	$110.27	$110.25	$110.30
Purchase #3	$66.82	8.493%	$72.495	$72.50	$72.50	$72.50
Purchase #4	$143.76	9.120%	$156.8709	$156.87	$156.85	$156.90
Purchase #5	$78.69	10.441%	$86.906	$86.91	$86.90	$86.90
Purchase #6	$149.59	12.322%	$168.0225	$168.02	$168.00	$168.00
Purchase #7	$197.58	8.713%	$214.7951	$214.80	$214.80	$214.80
7 purchase totals =	$879.06		$964.5115	$964.52	$964.45	$964.50