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	$201.40	3.119%	$207.6817	$207.68	$207.70	$207.70
Purchase #2	$169.76	12.843%	$191.5623	$191.56	$191.55	$191.60
Purchase #3	$115.29	7.488%	$123.9229	$123.92	$123.90	$123.90
Purchase #4	$188.38	4.131%	$196.162	$196.16	$196.15	$196.20
Purchase #5	$243.29	3.795%	$252.5229	$252.52	$252.50	$252.50
Purchase #6	$117.56	11.697%	$131.311	$131.31	$131.30	$131.30
Purchase #7	$87.29	11.815%	$97.6033	$97.60	$97.60	$97.60
7 purchase totals =	$1,122.97		$1,200.7661	$1,200.75	$1,200.70	$1,200.80