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	$90.39	9.190%	$98.6968	$98.70	$98.70	$98.70
Purchase #2	$183.53	7.827%	$197.8949	$197.89	$197.90	$197.90
Purchase #3	$93.33	7.676%	$100.494	$100.49	$100.50	$100.50
Purchase #4	$146.71	7.201%	$157.2746	$157.27	$157.25	$157.30
Purchase #5	$203.82	11.607%	$227.4774	$227.48	$227.50	$227.50
Purchase #6	$35.51	5.824%	$37.5781	$37.58	$37.60	$37.60
Purchase #7	$107.90	4.523%	$112.7803	$112.78	$112.80	$112.80
7 purchase totals =	$861.19		$932.1961	$932.19	$932.25	$932.30