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	$241.64	3.280%	$249.5658	$249.57	$249.55	$249.60
Purchase #2	$36.34	3.531%	$37.6232	$37.62	$37.60	$37.60
Purchase #3	$231.92	5.783%	$245.3319	$245.33	$245.35	$245.30
Purchase #4	$180.90	11.617%	$201.9152	$201.92	$201.90	$201.90
Purchase #5	$49.44	12.630%	$55.6843	$55.68	$55.70	$55.70
Purchase #6	$184.37	6.772%	$196.8555	$196.86	$196.85	$196.90
Purchase #7	$109.84	8.274%	$118.9282	$118.93	$118.95	$118.90
7 purchase totals =	$1,034.45		$1,105.9041	$1,105.91	$1,105.90	$1,105.90