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	$217.97	9.627%	$238.954	$238.95	$238.95	$239.00
Purchase #2	$213.26	11.639%	$238.0813	$238.08	$238.10	$238.10
Purchase #3	$55.45	7.379%	$59.5417	$59.54	$59.55	$59.50
Purchase #4	$226.83	10.389%	$250.3954	$250.40	$250.40	$250.40
Purchase #5	$157.73	13.725%	$179.3784	$179.38	$179.40	$179.40
Purchase #6	$92.98	11.671%	$103.8317	$103.83	$103.85	$103.80
Purchase #7	$212.41	13.229%	$240.5097	$240.51	$240.50	$240.50
7 purchase totals =	$1,176.63		$1,310.6922	$1,310.69	$1,310.75	$1,310.70