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	$82.61	12.199%	$92.6876	$92.69	$92.70	$92.70
Purchase #2	$38.63	12.243%	$43.3595	$43.36	$43.35	$43.40
Purchase #3	$12.32	9.760%	$13.5224	$13.52	$13.50	$13.50
Purchase #4	$186.27	10.661%	$206.1282	$206.13	$206.15	$206.10
Purchase #5	$242.85	4.379%	$253.4844	$253.48	$253.50	$253.50
Purchase #6	$160.32	11.401%	$178.5981	$178.60	$178.60	$178.60
Purchase #7	$208.78	5.769%	$220.8245	$220.82	$220.80	$220.80
7 purchase totals =	$931.78		$1,008.6047	$1,008.60	$1,008.60	$1,008.60