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	$214.61	7.628%	$230.9805	$230.98	$231.00	$231.00
Purchase #2	$36.82	4.362%	$38.4261	$38.43	$38.45	$38.40
Purchase #3	$17.38	8.273%	$18.8178	$18.82	$18.80	$18.80
Purchase #4	$230.88	7.392%	$247.9466	$247.95	$247.95	$247.90
Purchase #5	$93.58	13.169%	$105.9036	$105.90	$105.90	$105.90
Purchase #6	$181.83	4.838%	$190.6269	$190.63	$190.65	$190.60
Purchase #7	$160.33	6.711%	$171.0897	$171.09	$171.10	$171.10
7 purchase totals =	$935.43		$1,003.7912	$1,003.80	$1,003.85	$1,003.70