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	$219.44	13.735%	$249.5801	$249.58	$249.60	$249.60
Purchase #2	$98.94	4.720%	$103.61	$103.61	$103.60	$103.60
Purchase #3	$219.56	9.594%	$240.6246	$240.62	$240.60	$240.60
Purchase #4	$62.57	5.758%	$66.1728	$66.17	$66.15	$66.20
Purchase #5	$168.52	13.562%	$191.3747	$191.37	$191.35	$191.40
Purchase #6	$240.74	9.344%	$263.2347	$263.23	$263.25	$263.20
Purchase #7	$217.38	7.419%	$233.5074	$233.51	$233.50	$233.50
7 purchase totals =	$1,227.15		$1,348.1043	$1,348.09	$1,348.05	$1,348.10