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	$143.31	9.110%	$156.3655	$156.37	$156.35	$156.40
Purchase #2	$46.42	6.760%	$49.558	$49.56	$49.55	$49.60
Purchase #3	$169.45	5.339%	$178.4969	$178.50	$178.50	$178.50
Purchase #4	$85.38	4.552%	$89.2665	$89.27	$89.25	$89.30
Purchase #5	$107.94	9.688%	$118.3972	$118.40	$118.40	$118.40
Purchase #6	$18.96	6.865%	$20.2616	$20.26	$20.25	$20.30
Purchase #7	$139.56	6.429%	$148.5323	$148.53	$148.55	$148.50
7 purchase totals =	$711.02		$760.8780	$760.89	$760.85	$761.00