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	$128.60	10.572%	$142.1956	$142.20	$142.20	$142.20
Purchase #2	$36.91	12.314%	$41.4551	$41.46	$41.45	$41.50
Purchase #3	$244.89	4.164%	$255.0872	$255.09	$255.10	$255.10
Purchase #4	$109.43	3.518%	$113.2797	$113.28	$113.30	$113.30
Purchase #5	$196.54	10.773%	$217.7133	$217.71	$217.70	$217.70
Purchase #6	$77.48	8.211%	$83.8419	$83.84	$83.85	$83.80
Purchase #7	$157.92	9.307%	$172.6176	$172.62	$172.60	$172.60
7 purchase totals =	$951.77		$1,026.1904	$1,026.20	$1,026.20	$1,026.20