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	$122.55	9.612%	$134.3295	$134.33	$134.35	$134.30
Purchase #2	$33.94	9.803%	$37.2671	$37.27	$37.25	$37.30
Purchase #3	$189.76	3.520%	$196.4396	$196.44	$196.45	$196.40
Purchase #4	$159.34	8.312%	$172.5843	$172.58	$172.60	$172.60
Purchase #5	$144.94	12.151%	$162.5517	$162.55	$162.55	$162.60
Purchase #6	$156.84	8.792%	$170.6294	$170.63	$170.65	$170.60
Purchase #7	$197.27	8.317%	$213.6769	$213.68	$213.70	$213.70
7 purchase totals =	$1,004.64		$1,087.4785	$1,087.48	$1,087.55	$1,087.50