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	$103.82	5.553%	$109.5851	$109.59	$109.60	$109.60
Purchase #2	$163.43	11.261%	$181.8339	$181.83	$181.85	$181.80
Purchase #3	$119.61	13.149%	$135.3375	$135.34	$135.35	$135.30
Purchase #4	$76.46	11.691%	$85.3989	$85.40	$85.40	$85.40
Purchase #5	$245.68	5.530%	$259.2661	$259.27	$259.25	$259.30
Purchase #6	$73.26	13.798%	$83.3684	$83.37	$83.35	$83.40
Purchase #7	$128.47	13.114%	$145.3176	$145.32	$145.30	$145.30
7 purchase totals =	$910.73		$1,000.1075	$1,000.12	$1,000.10	$1,000.10