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	$36.46	6.613%	$38.8711	$38.87	$38.85	$38.90
Purchase #2	$16.99	3.513%	$17.5869	$17.59	$17.60	$17.60
Purchase #3	$210.45	7.334%	$225.8844	$225.88	$225.90	$225.90
Purchase #4	$202.81	6.368%	$215.7249	$215.72	$215.70	$215.70
Purchase #5	$66.48	9.607%	$72.8667	$72.87	$72.85	$72.90
Purchase #6	$72.57	13.269%	$82.1993	$82.20	$82.20	$82.20
Purchase #7	$66.52	7.334%	$71.3986	$71.40	$71.40	$71.40
7 purchase totals =	$672.28		$724.5319	$724.53	$724.50	$724.60