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	$46.56	12.703%	$52.4745	$52.47	$52.45	$52.50
Purchase #2	$60.93	10.332%	$67.2253	$67.23	$67.25	$67.20
Purchase #3	$50.82	11.364%	$56.5952	$56.60	$56.60	$56.60
Purchase #4	$98.61	11.478%	$109.9285	$109.93	$109.95	$109.90
Purchase #5	$137.95	8.350%	$149.4688	$149.47	$149.45	$149.50
Purchase #6	$218.32	10.714%	$241.7108	$241.71	$241.70	$241.70
Purchase #7	$106.38	11.570%	$118.6882	$118.69	$118.70	$118.70
7 purchase totals =	$719.57		$796.0913	$796.10	$796.10	$796.10