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	$59.45	10.455%	$65.6655	$65.67	$65.65	$65.70
Purchase #2	$49.78	4.318%	$51.9295	$51.93	$51.95	$51.90
Purchase #3	$152.53	9.726%	$167.3651	$167.37	$167.35	$167.40
Purchase #4	$176.67	12.852%	$199.3756	$199.38	$199.40	$199.40
Purchase #5	$244.62	10.511%	$270.332	$270.33	$270.35	$270.30
Purchase #6	$131.61	9.641%	$144.2985	$144.30	$144.30	$144.30
Purchase #7	$82.78	3.146%	$85.3843	$85.38	$85.40	$85.40
7 purchase totals =	$897.44		$984.3505	$984.36	$984.40	$984.40