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	$236.72	5.838%	$250.5397	$250.54	$250.55	$250.50
Purchase #2	$205.82	4.216%	$214.4974	$214.50	$214.50	$214.50
Purchase #3	$216.77	8.366%	$234.905	$234.91	$234.90	$234.90
Purchase #4	$37.74	5.808%	$39.9319	$39.93	$39.95	$39.90
Purchase #5	$91.66	9.104%	$100.0047	$100.00	$100.00	$100.00
Purchase #6	$142.54	9.621%	$156.2538	$156.25	$156.25	$156.30
Purchase #7	$5.72	6.403%	$6.0863	$6.09	$6.10	$6.10
7 purchase totals =	$936.97		$1,002.2188	$1,002.22	$1,002.25	$1,002.20