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	$239.89	3.308%	$247.8256	$247.83	$247.85	$247.80
Purchase #2	$187.40	11.111%	$208.222	$208.22	$208.20	$208.20
Purchase #3	$129.27	6.484%	$137.6519	$137.65	$137.65	$137.70
Purchase #4	$140.78	12.274%	$158.0593	$158.06	$158.05	$158.10
Purchase #5	$23.34	4.801%	$24.4606	$24.46	$24.45	$24.50
Purchase #6	$210.42	6.264%	$223.6007	$223.60	$223.60	$223.60
Purchase #7	$153.83	3.696%	$159.5156	$159.52	$159.50	$159.50
7 purchase totals =	$1,084.93		$1,159.3357	$1,159.34	$1,159.30	$1,159.40