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	$135.27	12.765%	$152.5372	$152.54	$152.55	$152.50
Purchase #2	$165.74	9.532%	$181.5383	$181.54	$181.55	$181.50
Purchase #3	$108.31	4.731%	$113.4341	$113.43	$113.45	$113.40
Purchase #4	$132.67	10.669%	$146.8246	$146.82	$146.80	$146.80
Purchase #5	$143.63	7.637%	$154.599	$154.60	$154.60	$154.60
Purchase #6	$117.26	5.694%	$123.9368	$123.94	$123.95	$123.90
Purchase #7	$92.94	3.377%	$96.0786	$96.08	$96.10	$96.10
7 purchase totals =	$895.82		$968.9486	$968.95	$969.00	$968.80