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	$186.90	5.112%	$196.4543	$196.45	$196.45	$196.50
Purchase #2	$216.92	13.187%	$245.5252	$245.53	$245.55	$245.50
Purchase #3	$21.59	3.693%	$22.3873	$22.39	$22.40	$22.40
Purchase #4	$213.54	13.364%	$242.0775	$242.08	$242.10	$242.10
Purchase #5	$197.60	8.765%	$214.9196	$214.92	$214.90	$214.90
Purchase #6	$229.38	11.440%	$255.6211	$255.62	$255.60	$255.60
Purchase #7	$159.39	7.255%	$170.9537	$170.95	$170.95	$171.00
7 purchase totals =	$1,225.32		$1,347.9387	$1,347.94	$1,347.95	$1,348.00