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	$204.55	7.365%	$219.6151	$219.62	$219.60	$219.60
Purchase #2	$162.32	10.627%	$179.5697	$179.57	$179.55	$179.60
Purchase #3	$158.89	12.357%	$178.524	$178.52	$178.50	$178.50
Purchase #4	$90.54	10.786%	$100.3056	$100.31	$100.30	$100.30
Purchase #5	$179.81	5.789%	$190.2192	$190.22	$190.20	$190.20
Purchase #6	$175.27	6.358%	$186.4137	$186.41	$186.40	$186.40
Purchase #7	$236.25	9.870%	$259.5679	$259.57	$259.55	$259.60
7 purchase totals =	$1,207.63		$1,314.2152	$1,314.22	$1,314.10	$1,314.20