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	$168.69	5.868%	$178.5887	$178.59	$178.60	$178.60
Purchase #2	$181.92	9.131%	$198.5311	$198.53	$198.55	$198.50
Purchase #3	$171.54	8.643%	$186.3662	$186.37	$186.35	$186.40
Purchase #4	$94.93	4.322%	$99.0329	$99.03	$99.05	$99.00
Purchase #5	$115.37	12.574%	$129.8766	$129.88	$129.90	$129.90
Purchase #6	$221.31	9.298%	$241.8874	$241.89	$241.90	$241.90
Purchase #7	$14.87	5.647%	$15.7097	$15.71	$15.70	$15.70
7 purchase totals =	$968.63		$1,049.9926	$1,050.00	$1,050.05	$1,050.00