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	$119.65	6.591%	$127.5361	$127.54	$127.55	$127.50
Purchase #2	$17.96	5.195%	$18.893	$18.89	$18.90	$18.90
Purchase #3	$72.69	10.643%	$80.4264	$80.43	$80.45	$80.40
Purchase #4	$20.26	12.396%	$22.7714	$22.77	$22.75	$22.80
Purchase #5	$230.38	5.723%	$243.5646	$243.56	$243.55	$243.60
Purchase #6	$192.77	3.755%	$200.0085	$200.01	$200.00	$200.00
Purchase #7	$176.95	3.184%	$182.5841	$182.58	$182.60	$182.60
7 purchase totals =	$830.66		$875.7841	$875.78	$875.80	$875.80