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	$86.79	7.611%	$93.3956	$93.40	$93.40	$93.40
Purchase #2	$29.34	10.650%	$32.4647	$32.46	$32.45	$32.50
Purchase #3	$162.60	12.514%	$182.9478	$182.95	$182.95	$182.90
Purchase #4	$190.97	10.624%	$211.2587	$211.26	$211.25	$211.30
Purchase #5	$130.32	11.462%	$145.2573	$145.26	$145.25	$145.30
Purchase #6	$81.58	9.371%	$89.2249	$89.22	$89.20	$89.20
Purchase #7	$168.75	6.348%	$179.4623	$179.46	$179.45	$179.50
7 purchase totals =	$850.35		$934.0113	$934.01	$933.95	$934.10