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	$127.67	13.558%	$144.9795	$144.98	$145.00	$145.00
Purchase #2	$15.64	11.582%	$17.4514	$17.45	$17.45	$17.50
Purchase #3	$155.34	13.225%	$175.8837	$175.88	$175.90	$175.90
Purchase #4	$203.26	3.367%	$210.1038	$210.10	$210.10	$210.10
Purchase #5	$154.88	10.695%	$171.4444	$171.44	$171.45	$171.40
Purchase #6	$146.29	8.589%	$158.8548	$158.85	$158.85	$158.90
Purchase #7	$38.95	9.292%	$42.5692	$42.57	$42.55	$42.60
7 purchase totals =	$842.03		$921.2868	$921.27	$921.30	$921.40