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	$211.25	8.778%	$229.7935	$229.79	$229.80	$229.80
Purchase #2	$52.72	13.102%	$59.6274	$59.63	$59.65	$59.60
Purchase #3	$68.64	7.307%	$73.6555	$73.66	$73.65	$73.70
Purchase #4	$162.81	3.698%	$168.8307	$168.83	$168.85	$168.80
Purchase #5	$231.99	7.103%	$248.4682	$248.47	$248.45	$248.50
Purchase #6	$52.72	12.199%	$59.1513	$59.15	$59.15	$59.20
Purchase #7	$176.29	7.315%	$189.1856	$189.19	$189.20	$189.20
7 purchase totals =	$956.42		$1,028.7122	$1,028.72	$1,028.75	$1,028.80