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	$64.95	7.512%	$69.829	$69.83	$69.85	$69.80
Purchase #2	$56.48	4.732%	$59.1526	$59.15	$59.15	$59.20
Purchase #3	$199.85	4.523%	$208.8892	$208.89	$208.90	$208.90
Purchase #4	$100.84	12.203%	$113.1455	$113.15	$113.15	$113.10
Purchase #5	$183.78	6.356%	$195.4611	$195.46	$195.45	$195.50
Purchase #6	$55.63	7.229%	$59.6515	$59.65	$59.65	$59.70
Purchase #7	$179.63	9.434%	$196.5763	$196.58	$196.60	$196.60
7 purchase totals =	$841.16		$902.7052	$902.71	$902.75	$902.80