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	$15.44	3.145%	$15.9256	$15.93	$15.95	$15.90
Purchase #2	$242.41	8.812%	$263.7712	$263.77	$263.75	$263.80
Purchase #3	$106.44	4.759%	$111.5055	$111.51	$111.50	$111.50
Purchase #4	$61.37	8.298%	$66.4625	$66.46	$66.45	$66.50
Purchase #5	$117.39	11.628%	$131.0401	$131.04	$131.05	$131.00
Purchase #6	$113.79	9.234%	$124.2974	$124.30	$124.30	$124.30
Purchase #7	$232.65	10.199%	$256.378	$256.38	$256.40	$256.40
7 purchase totals =	$889.49		$969.3803	$969.39	$969.40	$969.40