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	$39.35	4.757%	$41.2219	$41.22	$41.20	$41.20
Purchase #2	$70.27	13.286%	$79.6061	$79.61	$79.60	$79.60
Purchase #3	$208.68	11.110%	$231.8643	$231.86	$231.85	$231.90
Purchase #4	$241.65	9.454%	$264.4956	$264.50	$264.50	$264.50
Purchase #5	$107.28	8.549%	$116.4514	$116.45	$116.45	$116.50
Purchase #6	$242.99	7.648%	$261.5739	$261.57	$261.55	$261.60
Purchase #7	$53.73	10.357%	$59.2948	$59.29	$59.30	$59.30
7 purchase totals =	$963.95		$1,054.5080	$1,054.50	$1,054.45	$1,054.60