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	$241.40	11.373%	$268.8544	$268.85	$268.85	$268.90
Purchase #2	$116.29	4.353%	$121.3521	$121.35	$121.35	$121.40
Purchase #3	$59.66	3.308%	$61.6336	$61.63	$61.65	$61.60
Purchase #4	$223.48	4.654%	$233.8808	$233.88	$233.90	$233.90
Purchase #5	$35.77	11.510%	$39.8871	$39.89	$39.90	$39.90
Purchase #6	$43.75	6.819%	$46.7333	$46.73	$46.75	$46.70
Purchase #7	$176.71	12.233%	$198.3269	$198.33	$198.35	$198.30
7 purchase totals =	$897.06		$970.6682	$970.66	$970.75	$970.70