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	$226.58	12.487%	$254.873	$254.87	$254.85	$254.90
Purchase #2	$249.69	4.744%	$261.5353	$261.54	$261.55	$261.50
Purchase #3	$143.71	13.305%	$162.8306	$162.83	$162.85	$162.80
Purchase #4	$64.47	10.547%	$71.2697	$71.27	$71.25	$71.30
Purchase #5	$47.84	12.842%	$53.9836	$53.98	$54.00	$54.00
Purchase #6	$153.97	9.773%	$169.0175	$169.02	$169.00	$169.00
Purchase #7	$156.49	12.822%	$176.5551	$176.56	$176.55	$176.60
7 purchase totals =	$1,042.75		$1,150.0648	$1,150.07	$1,150.05	$1,150.10