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	$164.87	9.230%	$180.0875	$180.09	$180.10	$180.10
Purchase #2	$134.63	4.801%	$141.0936	$141.09	$141.10	$141.10
Purchase #3	$78.93	4.493%	$82.4763	$82.48	$82.50	$82.50
Purchase #4	$170.79	12.151%	$191.5427	$191.54	$191.55	$191.50
Purchase #5	$184.69	12.450%	$207.6839	$207.68	$207.70	$207.70
Purchase #6	$99.76	4.565%	$104.314	$104.31	$104.30	$104.30
Purchase #7	$35.70	12.294%	$40.089	$40.09	$40.10	$40.10
7 purchase totals =	$869.37		$947.2870	$947.28	$947.35	$947.30