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	$46.32	13.269%	$52.4662	$52.47	$52.45	$52.50
Purchase #2	$147.58	3.592%	$152.8811	$152.88	$152.90	$152.90
Purchase #3	$74.77	13.188%	$84.6307	$84.63	$84.65	$84.60
Purchase #4	$57.72	7.730%	$62.1818	$62.18	$62.20	$62.20
Purchase #5	$235.85	12.584%	$265.5294	$265.53	$265.55	$265.50
Purchase #6	$169.77	4.152%	$176.8189	$176.82	$176.80	$176.80
Purchase #7	$93.78	11.866%	$104.9079	$104.91	$104.90	$104.90
7 purchase totals =	$825.79		$899.4160	$899.42	$899.45	$899.40