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	$218.73	8.598%	$237.5364	$237.54	$237.55	$237.50
Purchase #2	$69.95	12.176%	$78.4671	$78.47	$78.45	$78.50
Purchase #3	$102.84	5.830%	$108.8356	$108.84	$108.85	$108.80
Purchase #4	$242.51	7.198%	$259.9659	$259.97	$259.95	$260.00
Purchase #5	$145.47	13.570%	$165.2103	$165.21	$165.20	$165.20
Purchase #6	$96.34	4.522%	$100.6965	$100.70	$100.70	$100.70
Purchase #7	$131.46	6.147%	$139.5408	$139.54	$139.55	$139.50
7 purchase totals =	$1,007.30		$1,090.2526	$1,090.27	$1,090.25	$1,090.20