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	$162.68	3.593%	$168.5251	$168.53	$168.55	$168.50
Purchase #2	$92.75	5.254%	$97.6231	$97.62	$97.60	$97.60
Purchase #3	$76.80	7.442%	$82.5155	$82.52	$82.50	$82.50
Purchase #4	$205.81	9.364%	$225.082	$225.08	$225.10	$225.10
Purchase #5	$12.85	10.738%	$14.2298	$14.23	$14.25	$14.20
Purchase #6	$37.91	6.651%	$40.4314	$40.43	$40.45	$40.40
Purchase #7	$127.95	11.492%	$142.654	$142.65	$142.65	$142.70
7 purchase totals =	$716.75		$771.0609	$771.06	$771.10	$771.00