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	$158.38	10.102%	$174.3795	$174.38	$174.40	$174.40
Purchase #2	$59.49	4.118%	$61.9398	$61.94	$61.95	$61.90
Purchase #3	$77.83	6.546%	$82.9248	$82.92	$82.90	$82.90
Purchase #4	$212.66	3.494%	$220.0903	$220.09	$220.10	$220.10
Purchase #5	$26.82	4.167%	$27.9376	$27.94	$27.95	$27.90
Purchase #6	$241.56	11.554%	$269.4698	$269.47	$269.45	$269.50
Purchase #7	$113.88	3.538%	$117.9091	$117.91	$117.90	$117.90
7 purchase totals =	$890.62		$954.6509	$954.65	$954.65	$954.60