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	$210.96	5.164%	$221.854	$221.85	$221.85	$221.90
Purchase #2	$200.42	11.815%	$224.0996	$224.10	$224.10	$224.10
Purchase #3	$154.75	6.324%	$164.5364	$164.54	$164.55	$164.50
Purchase #4	$153.93	5.522%	$162.43	$162.43	$162.45	$162.40
Purchase #5	$31.91	4.786%	$33.4372	$33.44	$33.45	$33.40
Purchase #6	$155.72	7.113%	$166.7964	$166.80	$166.80	$166.80
Purchase #7	$145.42	3.466%	$150.4603	$150.46	$150.45	$150.50
7 purchase totals =	$1,053.11		$1,123.6139	$1,123.62	$1,123.65	$1,123.60