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	$43.52	9.136%	$47.496	$47.50	$47.50	$47.50
Purchase #2	$38.93	11.565%	$43.4323	$43.43	$43.45	$43.40
Purchase #3	$92.52	9.847%	$101.6304	$101.63	$101.65	$101.60
Purchase #4	$213.91	3.521%	$221.4418	$221.44	$221.45	$221.40
Purchase #5	$248.69	9.557%	$272.4573	$272.46	$272.45	$272.50
Purchase #6	$96.54	5.537%	$101.8854	$101.89	$101.90	$101.90
Purchase #7	$9.60	11.145%	$10.6699	$10.67	$10.65	$10.70
7 purchase totals =	$743.71		$799.0131	$799.02	$799.05	$799.00