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	$68.83	4.677%	$72.0492	$72.05	$72.05	$72.00
Purchase #2	$247.72	5.546%	$261.4586	$261.46	$261.45	$261.50
Purchase #3	$34.94	3.809%	$36.2709	$36.27	$36.25	$36.30
Purchase #4	$247.73	3.675%	$256.8341	$256.83	$256.85	$256.80
Purchase #5	$128.94	7.866%	$139.0824	$139.08	$139.10	$139.10
Purchase #6	$174.34	9.147%	$190.2869	$190.29	$190.30	$190.30
Purchase #7	$38.67	6.601%	$41.2226	$41.22	$41.20	$41.20
7 purchase totals =	$941.17		$997.2047	$997.20	$997.20	$997.20