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	$56.37	11.448%	$62.8232	$62.82	$62.80	$62.80
Purchase #2	$148.45	12.760%	$167.3922	$167.39	$167.40	$167.40
Purchase #3	$158.33	8.163%	$171.2545	$171.25	$171.25	$171.30
Purchase #4	$39.59	5.780%	$41.8783	$41.88	$41.90	$41.90
Purchase #5	$23.75	3.782%	$24.6482	$24.65	$24.65	$24.60
Purchase #6	$29.58	6.490%	$31.4997	$31.50	$31.50	$31.50
Purchase #7	$227.77	3.294%	$235.2727	$235.27	$235.25	$235.30
7 purchase totals =	$683.84		$734.7688	$734.76	$734.75	$734.80