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	$183.52	11.630%	$204.8634	$204.86	$204.85	$204.90
Purchase #2	$222.48	10.177%	$245.1218	$245.12	$245.10	$245.10
Purchase #3	$113.51	13.238%	$128.5365	$128.54	$128.55	$128.50
Purchase #4	$10.89	4.138%	$11.3406	$11.34	$11.35	$11.30
Purchase #5	$71.39	7.820%	$76.9727	$76.97	$76.95	$77.00
Purchase #6	$247.54	7.787%	$266.8159	$266.82	$266.80	$266.80
Purchase #7	$66.56	5.684%	$70.3433	$70.34	$70.35	$70.30
7 purchase totals =	$915.89		$1,003.9942	$1,003.99	$1,003.95	$1,003.90