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	$156.65	5.869%	$165.8438	$165.84	$165.85	$165.80
Purchase #2	$62.71	11.122%	$69.6846	$69.68	$69.70	$69.70
Purchase #3	$129.32	10.868%	$143.3745	$143.37	$143.35	$143.40
Purchase #4	$75.91	3.231%	$78.3627	$78.36	$78.35	$78.40
Purchase #5	$111.40	6.417%	$118.5485	$118.55	$118.55	$118.50
Purchase #6	$248.73	9.332%	$271.9415	$271.94	$271.95	$271.90
Purchase #7	$162.58	4.388%	$169.714	$169.71	$169.70	$169.70
7 purchase totals =	$947.30		$1,017.4696	$1,017.45	$1,017.45	$1,017.40