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	$192.80	5.422%	$203.2536	$203.25	$203.25	$203.30
Purchase #2	$57.26	7.448%	$61.5247	$61.52	$61.50	$61.50
Purchase #3	$29.93	12.635%	$33.7117	$33.71	$33.70	$33.70
Purchase #4	$112.38	10.128%	$123.7618	$123.76	$123.75	$123.80
Purchase #5	$248.60	6.715%	$265.2935	$265.29	$265.30	$265.30
Purchase #6	$78.27	13.478%	$88.8192	$88.82	$88.80	$88.80
Purchase #7	$246.57	13.133%	$278.952	$278.95	$278.95	$279.00
7 purchase totals =	$965.81		$1,055.3165	$1,055.30	$1,055.25	$1,055.40