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	$181.27	13.198%	$205.194	$205.19	$205.20	$205.20
Purchase #2	$104.54	3.479%	$108.1769	$108.18	$108.20	$108.20
Purchase #3	$96.34	7.343%	$103.4142	$103.41	$103.40	$103.40
Purchase #4	$158.93	4.412%	$165.942	$165.94	$165.95	$165.90
Purchase #5	$66.98	3.813%	$69.5339	$69.53	$69.55	$69.50
Purchase #6	$230.59	10.859%	$255.6298	$255.63	$255.65	$255.60
Purchase #7	$169.91	6.843%	$181.5369	$181.54	$181.55	$181.50
7 purchase totals =	$1,008.56		$1,089.4277	$1,089.42	$1,089.50	$1,089.30