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	$52.41	7.653%	$56.4209	$56.42	$56.40	$56.40
Purchase #2	$17.84	4.402%	$18.6253	$18.63	$18.65	$18.60
Purchase #3	$223.44	4.277%	$232.9965	$233.00	$233.00	$233.00
Purchase #4	$30.84	6.614%	$32.8798	$32.88	$32.90	$32.90
Purchase #5	$103.41	8.224%	$111.9144	$111.91	$111.90	$111.90
Purchase #6	$133.72	7.605%	$143.8894	$143.89	$143.90	$143.90
Purchase #7	$198.29	12.453%	$222.9831	$222.98	$223.00	$223.00
7 purchase totals =	$759.95		$819.7094	$819.71	$819.75	$819.70