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	$48.56	5.504%	$51.2327	$51.23	$51.25	$51.20
Purchase #2	$90.89	11.527%	$101.3669	$101.37	$101.35	$101.40
Purchase #3	$102.29	11.713%	$114.2712	$114.27	$114.25	$114.30
Purchase #4	$159.25	13.381%	$180.5592	$180.56	$180.55	$180.60
Purchase #5	$5.55	10.729%	$6.1455	$6.15	$6.15	$6.10
Purchase #6	$194.52	10.210%	$214.3805	$214.38	$214.40	$214.40
Purchase #7	$105.85	6.160%	$112.3704	$112.37	$112.35	$112.40
7 purchase totals =	$706.91		$780.3264	$780.33	$780.30	$780.40