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	$217.72	3.220%	$224.7306	$224.73	$224.75	$224.70
Purchase #2	$123.26	3.296%	$127.3226	$127.32	$127.30	$127.30
Purchase #3	$135.70	6.705%	$144.7987	$144.80	$144.80	$144.80
Purchase #4	$102.25	3.357%	$105.6825	$105.68	$105.70	$105.70
Purchase #5	$16.84	11.108%	$18.7106	$18.71	$18.70	$18.70
Purchase #6	$184.54	5.417%	$194.5365	$194.54	$194.55	$194.50
Purchase #7	$109.75	12.345%	$123.2986	$123.30	$123.30	$123.30
7 purchase totals =	$890.06		$939.0801	$939.08	$939.10	$939.00