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	$209.43	7.361%	$224.8461	$224.85	$224.85	$224.80
Purchase #2	$167.45	10.409%	$184.8799	$184.88	$184.90	$184.90
Purchase #3	$40.38	8.780%	$43.9254	$43.93	$43.95	$43.90
Purchase #4	$65.60	6.278%	$69.7184	$69.72	$69.70	$69.70
Purchase #5	$18.32	12.434%	$20.5979	$20.60	$20.60	$20.60
Purchase #6	$48.76	7.314%	$52.3263	$52.33	$52.35	$52.30
Purchase #7	$139.59	5.536%	$147.3177	$147.32	$147.30	$147.30
7 purchase totals =	$689.53		$743.6117	$743.63	$743.65	$743.50