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	$157.93	3.158%	$162.9174	$162.92	$162.90	$162.90
Purchase #2	$210.48	5.174%	$221.3702	$221.37	$221.35	$221.40
Purchase #3	$112.52	12.738%	$126.8528	$126.85	$126.85	$126.90
Purchase #4	$17.99	4.304%	$18.7643	$18.76	$18.75	$18.80
Purchase #5	$53.65	8.738%	$58.3379	$58.34	$58.35	$58.30
Purchase #6	$245.86	3.841%	$255.3035	$255.30	$255.30	$255.30
Purchase #7	$145.69	13.182%	$164.8949	$164.89	$164.90	$164.90
7 purchase totals =	$944.12		$1,008.4410	$1,008.43	$1,008.40	$1,008.50