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	$177.73	7.687%	$191.3921	$191.39	$191.40	$191.40
Purchase #2	$96.77	3.703%	$100.3534	$100.35	$100.35	$100.40
Purchase #3	$187.38	3.211%	$193.3968	$193.40	$193.40	$193.40
Purchase #4	$30.82	13.242%	$34.9012	$34.90	$34.90	$34.90
Purchase #5	$127.61	12.390%	$143.4209	$143.42	$143.40	$143.40
Purchase #6	$232.56	10.181%	$256.2369	$256.24	$256.25	$256.20
Purchase #7	$132.55	6.254%	$140.8397	$140.84	$140.85	$140.80
7 purchase totals =	$985.42		$1,060.5410	$1,060.54	$1,060.55	$1,060.50