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	$73.89	4.641%	$77.3192	$77.32	$77.30	$77.30
Purchase #2	$41.52	5.812%	$43.9331	$43.93	$43.95	$43.90
Purchase #3	$75.31	13.701%	$85.6282	$85.63	$85.65	$85.60
Purchase #4	$74.46	10.495%	$82.2746	$82.27	$82.25	$82.30
Purchase #5	$108.68	13.621%	$123.4833	$123.48	$123.50	$123.50
Purchase #6	$182.37	8.374%	$197.6417	$197.64	$197.65	$197.60
Purchase #7	$79.59	3.612%	$82.4648	$82.46	$82.45	$82.50
7 purchase totals =	$635.82		$692.7449	$692.73	$692.75	$692.70