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	$199.35	5.295%	$209.9056	$209.91	$209.90	$209.90
Purchase #2	$78.25	11.671%	$87.3826	$87.38	$87.40	$87.40
Purchase #3	$182.79	3.342%	$188.8988	$188.90	$188.90	$188.90
Purchase #4	$51.57	11.307%	$57.401	$57.40	$57.40	$57.40
Purchase #5	$121.46	9.315%	$132.774	$132.77	$132.75	$132.80
Purchase #6	$128.53	12.404%	$144.4729	$144.47	$144.45	$144.50
Purchase #7	$100.39	5.222%	$105.6324	$105.63	$105.65	$105.60
7 purchase totals =	$862.34		$926.4673	$926.46	$926.45	$926.50