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	$196.71	4.393%	$205.3515	$205.35	$205.35	$205.40
Purchase #2	$34.73	7.836%	$37.4514	$37.45	$37.45	$37.50
Purchase #3	$42.79	7.356%	$45.9376	$45.94	$45.95	$45.90
Purchase #4	$181.54	13.632%	$206.2875	$206.29	$206.30	$206.30
Purchase #5	$129.35	5.771%	$136.8148	$136.81	$136.80	$136.80
Purchase #6	$110.28	12.314%	$123.8599	$123.86	$123.85	$123.90
Purchase #7	$47.38	3.510%	$49.043	$49.04	$49.05	$49.00
7 purchase totals =	$742.78		$804.7457	$804.74	$804.75	$804.80