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	$185.30	8.552%	$201.1469	$201.15	$201.15	$201.10
Purchase #2	$50.26	11.131%	$55.8544	$55.85	$55.85	$55.90
Purchase #3	$137.96	13.324%	$156.3418	$156.34	$156.35	$156.30
Purchase #4	$31.75	12.241%	$35.6365	$35.64	$35.65	$35.60
Purchase #5	$52.92	13.236%	$59.9245	$59.92	$59.90	$59.90
Purchase #6	$60.94	9.281%	$66.5958	$66.60	$66.60	$66.60
Purchase #7	$176.57	11.190%	$196.3282	$196.33	$196.35	$196.30
7 purchase totals =	$695.70		$771.8281	$771.83	$771.85	$771.70