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	$227.69	6.500%	$242.4899	$242.49	$242.50	$242.50
Purchase #2	$20.44	4.500%	$21.3598	$21.36	$21.35	$21.40
Purchase #3	$116.78	5.579%	$123.2952	$123.30	$123.30	$123.30
Purchase #4	$201.44	12.680%	$226.9826	$226.98	$227.00	$227.00
Purchase #5	$50.87	9.199%	$55.5495	$55.55	$55.55	$55.50
Purchase #6	$51.40	8.475%	$55.7562	$55.76	$55.75	$55.80
Purchase #7	$91.28	9.666%	$100.1031	$100.10	$100.10	$100.10
7 purchase totals =	$759.90		$825.5363	$825.54	$825.55	$825.60