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	$203.87	5.640%	$215.3683	$215.37	$215.35	$215.40
Purchase #2	$45.81	4.734%	$47.9786	$47.98	$48.00	$48.00
Purchase #3	$145.27	4.163%	$151.3176	$151.32	$151.30	$151.30
Purchase #4	$179.90	9.403%	$196.816	$196.82	$196.80	$196.80
Purchase #5	$74.69	3.737%	$77.4812	$77.48	$77.50	$77.50
Purchase #6	$52.34	9.467%	$57.295	$57.30	$57.30	$57.30
Purchase #7	$105.72	7.405%	$113.5486	$113.55	$113.55	$113.50
7 purchase totals =	$807.60		$859.8053	$859.82	$859.80	$859.80