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	$56.90	5.411%	$59.9789	$59.98	$60.00	$60.00
Purchase #2	$133.44	7.120%	$142.9409	$142.94	$142.95	$142.90
Purchase #3	$137.50	4.840%	$144.155	$144.16	$144.15	$144.20
Purchase #4	$163.75	7.744%	$176.4308	$176.43	$176.45	$176.40
Purchase #5	$89.43	12.424%	$100.5408	$100.54	$100.55	$100.50
Purchase #6	$36.61	3.304%	$37.8196	$37.82	$37.80	$37.80
Purchase #7	$187.85	4.695%	$196.6696	$196.67	$196.65	$196.70
7 purchase totals =	$805.48		$858.5356	$858.54	$858.55	$858.50