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	$222.54	4.702%	$233.0038	$233.00	$233.00	$233.00
Purchase #2	$162.58	8.462%	$176.3375	$176.34	$176.35	$176.30
Purchase #3	$243.47	7.629%	$262.0443	$262.04	$262.05	$262.00
Purchase #4	$149.69	4.488%	$156.4081	$156.41	$156.40	$156.40
Purchase #5	$52.80	3.297%	$54.5408	$54.54	$54.55	$54.50
Purchase #6	$60.32	7.501%	$64.8446	$64.84	$64.85	$64.80
Purchase #7	$222.70	4.837%	$233.472	$233.47	$233.45	$233.50
7 purchase totals =	$1,114.10		$1,180.6511	$1,180.64	$1,180.65	$1,180.50