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	$84.45	9.269%	$92.2777	$92.28	$92.30	$92.30
Purchase #2	$220.35	7.671%	$237.253	$237.25	$237.25	$237.30
Purchase #3	$236.77	7.812%	$255.2665	$255.27	$255.25	$255.30
Purchase #4	$160.31	12.177%	$179.8309	$179.83	$179.85	$179.80
Purchase #5	$218.34	10.539%	$241.3509	$241.35	$241.35	$241.40
Purchase #6	$225.45	13.415%	$255.6941	$255.69	$255.70	$255.70
Purchase #7	$153.50	7.451%	$164.9373	$164.94	$164.95	$164.90
7 purchase totals =	$1,299.17		$1,426.6104	$1,426.61	$1,426.65	$1,426.70