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	$222.36	3.822%	$230.8586	$230.86	$230.85	$230.90
Purchase #2	$53.84	8.797%	$58.5763	$58.58	$58.60	$58.60
Purchase #3	$141.59	6.598%	$150.9321	$150.93	$150.95	$150.90
Purchase #4	$245.94	3.664%	$254.9512	$254.95	$254.95	$255.00
Purchase #5	$171.40	13.579%	$194.6744	$194.67	$194.65	$194.70
Purchase #6	$40.82	4.618%	$42.7051	$42.71	$42.70	$42.70
Purchase #7	$131.55	9.155%	$143.5934	$143.59	$143.60	$143.60
7 purchase totals =	$1,007.50		$1,076.2911	$1,076.29	$1,076.30	$1,076.40