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	$160.94	5.149%	$169.2268	$169.23	$169.25	$169.20
Purchase #2	$103.99	7.623%	$111.9172	$111.92	$111.90	$111.90
Purchase #3	$38.77	10.614%	$42.885	$42.89	$42.90	$42.90
Purchase #4	$191.32	11.345%	$213.0253	$213.03	$213.05	$213.00
Purchase #5	$24.84	11.247%	$27.6338	$27.63	$27.65	$27.60
Purchase #6	$50.79	6.156%	$53.9166	$53.92	$53.90	$53.90
Purchase #7	$34.95	13.792%	$39.7703	$39.77	$39.75	$39.80
7 purchase totals =	$605.60		$658.3750	$658.39	$658.40	$658.30