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	$100.71	3.622%	$104.3577	$104.36	$104.35	$104.40
Purchase #2	$6.60	13.822%	$7.5123	$7.51	$7.50	$7.50
Purchase #3	$171.52	6.140%	$182.0513	$182.05	$182.05	$182.10
Purchase #4	$166.41	4.517%	$173.9267	$173.93	$173.95	$173.90
Purchase #5	$64.75	4.841%	$67.8845	$67.88	$67.90	$67.90
Purchase #6	$61.52	9.257%	$67.2149	$67.21	$67.20	$67.20
Purchase #7	$28.86	5.531%	$30.4562	$30.46	$30.45	$30.50
7 purchase totals =	$600.37		$633.4036	$633.40	$633.40	$633.50