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	$64.27	12.342%	$72.2022	$72.20	$72.20	$72.20
Purchase #2	$39.66	4.396%	$41.4035	$41.40	$41.40	$41.40
Purchase #3	$206.90	4.219%	$215.6291	$215.63	$215.65	$215.60
Purchase #4	$129.43	7.515%	$139.1567	$139.16	$139.15	$139.20
Purchase #5	$49.47	4.578%	$51.7347	$51.73	$51.75	$51.70
Purchase #6	$138.78	10.390%	$153.1992	$153.20	$153.20	$153.20
Purchase #7	$72.69	13.409%	$82.437	$82.44	$82.45	$82.40
7 purchase totals =	$701.20		$755.7624	$755.76	$755.80	$755.70