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	$68.93	4.530%	$72.0525	$72.05	$72.05	$72.10
Purchase #2	$52.90	4.789%	$55.4334	$55.43	$55.45	$55.40
Purchase #3	$244.48	3.114%	$252.0931	$252.09	$252.10	$252.10
Purchase #4	$26.56	5.106%	$27.9162	$27.92	$27.90	$27.90
Purchase #5	$73.81	11.439%	$82.2531	$82.25	$82.25	$82.30
Purchase #6	$105.96	10.794%	$117.3973	$117.40	$117.40	$117.40
Purchase #7	$93.87	5.735%	$99.2534	$99.25	$99.25	$99.30
7 purchase totals =	$666.51		$706.3990	$706.39	$706.40	$706.50