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	$170.27	6.558%	$181.4363	$181.44	$181.45	$181.40
Purchase #2	$146.55	4.495%	$153.1374	$153.14	$153.15	$153.10
Purchase #3	$171.83	9.409%	$187.9975	$188.00	$188.00	$188.00
Purchase #4	$84.63	7.344%	$90.8452	$90.85	$90.85	$90.80
Purchase #5	$116.90	5.840%	$123.727	$123.73	$123.75	$123.70
Purchase #6	$128.53	11.840%	$143.748	$143.75	$143.75	$143.70
Purchase #7	$150.31	3.641%	$155.7828	$155.78	$155.80	$155.80
7 purchase totals =	$969.02		$1,036.6742	$1,036.69	$1,036.75	$1,036.50