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	$125.82	13.390%	$142.6673	$142.67	$142.65	$142.70
Purchase #2	$60.55	8.824%	$65.8929	$65.89	$65.90	$65.90
Purchase #3	$89.88	11.811%	$100.4957	$100.50	$100.50	$100.50
Purchase #4	$153.69	5.602%	$162.2997	$162.30	$162.30	$162.30
Purchase #5	$66.61	4.674%	$69.7234	$69.72	$69.70	$69.70
Purchase #6	$233.69	11.343%	$260.1975	$260.20	$260.20	$260.20
Purchase #7	$142.56	9.616%	$156.2686	$156.27	$156.25	$156.30
7 purchase totals =	$872.80		$957.5451	$957.55	$957.50	$957.60