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	$214.78	9.520%	$235.2271	$235.23	$235.25	$235.20
Purchase #2	$136.69	12.207%	$153.3757	$153.38	$153.40	$153.40
Purchase #3	$184.86	10.447%	$204.1723	$204.17	$204.15	$204.20
Purchase #4	$76.35	3.342%	$78.9016	$78.90	$78.90	$78.90
Purchase #5	$47.37	8.770%	$51.5243	$51.52	$51.50	$51.50
Purchase #6	$113.48	6.543%	$120.905	$120.91	$120.90	$120.90
Purchase #7	$231.71	7.803%	$249.7903	$249.79	$249.80	$249.80
7 purchase totals =	$1,005.24		$1,093.8963	$1,093.90	$1,093.90	$1,093.90