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	$30.95	6.531%	$32.9713	$32.97	$32.95	$33.00
Purchase #2	$73.53	9.122%	$80.2374	$80.24	$80.25	$80.20
Purchase #3	$213.91	9.228%	$233.6496	$233.65	$233.65	$233.60
Purchase #4	$226.25	5.235%	$238.0942	$238.09	$238.10	$238.10
Purchase #5	$72.68	8.289%	$78.7044	$78.70	$78.70	$78.70
Purchase #6	$249.55	6.411%	$265.5487	$265.55	$265.55	$265.50
Purchase #7	$76.51	11.393%	$85.2268	$85.23	$85.25	$85.20
7 purchase totals =	$943.38		$1,014.4324	$1,014.43	$1,014.45	$1,014.30