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	$178.31	7.553%	$191.7778	$191.78	$191.80	$191.80
Purchase #2	$149.93	5.774%	$158.587	$158.59	$158.60	$158.60
Purchase #3	$188.99	13.515%	$214.532	$214.53	$214.55	$214.50
Purchase #4	$176.80	11.226%	$196.6476	$196.65	$196.65	$196.60
Purchase #5	$185.70	13.724%	$211.1855	$211.19	$211.20	$211.20
Purchase #6	$86.79	6.318%	$92.2734	$92.27	$92.25	$92.30
Purchase #7	$54.55	13.410%	$61.8652	$61.87	$61.85	$61.90
7 purchase totals =	$1,021.07		$1,126.8685	$1,126.88	$1,126.90	$1,126.90