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	$137.81	10.213%	$151.8845	$151.88	$151.90	$151.90
Purchase #2	$181.44	6.155%	$192.6076	$192.61	$192.60	$192.60
Purchase #3	$148.39	13.729%	$168.7625	$168.76	$168.75	$168.80
Purchase #4	$49.62	4.110%	$51.6594	$51.66	$51.65	$51.70
Purchase #5	$137.63	11.673%	$153.6955	$153.70	$153.70	$153.70
Purchase #6	$242.94	10.291%	$267.941	$267.94	$267.95	$267.90
Purchase #7	$172.78	5.342%	$182.0099	$182.01	$182.00	$182.00
7 purchase totals =	$1,070.61		$1,168.5604	$1,168.56	$1,168.55	$1,168.60