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	$126.73	10.663%	$140.2432	$140.24	$140.25	$140.20
Purchase #2	$234.88	3.277%	$242.577	$242.58	$242.60	$242.60
Purchase #3	$141.90	7.417%	$152.4247	$152.42	$152.40	$152.40
Purchase #4	$187.32	4.869%	$196.4406	$196.44	$196.45	$196.40
Purchase #5	$158.64	3.124%	$163.5959	$163.60	$163.60	$163.60
Purchase #6	$16.47	12.373%	$18.5078	$18.51	$18.50	$18.50
Purchase #7	$185.60	13.333%	$210.346	$210.35	$210.35	$210.30
7 purchase totals =	$1,051.54		$1,124.1352	$1,124.14	$1,124.15	$1,124.00