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	$84.90	5.417%	$89.499	$89.50	$89.50	$89.50
Purchase #2	$32.81	6.514%	$34.9472	$34.95	$34.95	$34.90
Purchase #3	$19.55	12.292%	$21.9531	$21.95	$21.95	$22.00
Purchase #4	$116.32	11.210%	$129.3595	$129.36	$129.35	$129.40
Purchase #5	$16.72	12.806%	$18.8612	$18.86	$18.85	$18.90
Purchase #6	$200.79	8.824%	$218.5077	$218.51	$218.50	$218.50
Purchase #7	$93.46	7.476%	$100.4471	$100.45	$100.45	$100.40
7 purchase totals =	$564.55		$613.5748	$613.58	$613.55	$613.60