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	$212.98	7.777%	$229.5435	$229.54	$229.55	$229.50
Purchase #2	$211.55	12.783%	$238.5924	$238.59	$238.60	$238.60
Purchase #3	$78.51	12.730%	$88.5043	$88.50	$88.50	$88.50
Purchase #4	$168.34	10.246%	$185.5881	$185.59	$185.60	$185.60
Purchase #5	$208.40	11.142%	$231.6199	$231.62	$231.60	$231.60
Purchase #6	$60.39	10.630%	$66.8095	$66.81	$66.80	$66.80
Purchase #7	$47.29	8.519%	$51.3186	$51.32	$51.30	$51.30
7 purchase totals =	$987.46		$1,091.9763	$1,091.97	$1,091.95	$1,091.90