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	$219.38	6.274%	$233.1439	$233.14	$233.15	$233.10
Purchase #2	$169.27	6.141%	$179.6649	$179.66	$179.65	$179.70
Purchase #3	$113.53	8.513%	$123.1948	$123.19	$123.20	$123.20
Purchase #4	$194.39	12.394%	$218.4827	$218.48	$218.50	$218.50
Purchase #5	$95.57	9.552%	$104.6988	$104.70	$104.70	$104.70
Purchase #6	$127.45	9.353%	$139.3704	$139.37	$139.35	$139.40
Purchase #7	$58.41	7.791%	$62.9607	$62.96	$62.95	$63.00
7 purchase totals =	$978.00		$1,061.5162	$1,061.50	$1,061.50	$1,061.60