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	$80.70	10.820%	$89.4317	$89.43	$89.45	$89.40
Purchase #2	$191.38	3.629%	$198.3252	$198.33	$198.35	$198.30
Purchase #3	$127.84	11.326%	$142.3192	$142.32	$142.30	$142.30
Purchase #4	$158.46	6.315%	$168.4667	$168.47	$168.45	$168.50
Purchase #5	$46.41	12.412%	$52.1704	$52.17	$52.15	$52.20
Purchase #6	$108.99	8.211%	$117.9392	$117.94	$117.95	$117.90
Purchase #7	$229.45	4.589%	$239.9795	$239.98	$240.00	$240.00
7 purchase totals =	$943.23		$1,008.6319	$1,008.64	$1,008.65	$1,008.60