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	$48.66	6.777%	$51.9577	$51.96	$51.95	$52.00
Purchase #2	$228.45	5.461%	$240.9257	$240.93	$240.95	$240.90
Purchase #3	$103.62	7.418%	$111.3065	$111.31	$111.30	$111.30
Purchase #4	$5.94	10.746%	$6.5783	$6.58	$6.60	$6.60
Purchase #5	$234.41	9.805%	$257.3939	$257.39	$257.40	$257.40
Purchase #6	$190.58	5.120%	$200.3377	$200.34	$200.35	$200.30
Purchase #7	$124.95	5.530%	$131.8597	$131.86	$131.85	$131.90
7 purchase totals =	$936.61		$1,000.3595	$1,000.37	$1,000.40	$1,000.40