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	$78.30	10.189%	$86.278	$86.28	$86.30	$86.30
Purchase #2	$116.51	10.273%	$128.4791	$128.48	$128.50	$128.50
Purchase #3	$122.98	11.736%	$137.4129	$137.41	$137.40	$137.40
Purchase #4	$189.88	3.737%	$196.9758	$196.98	$197.00	$197.00
Purchase #5	$165.48	4.387%	$172.7396	$172.74	$172.75	$172.70
Purchase #6	$142.54	8.364%	$154.462	$154.46	$154.45	$154.50
Purchase #7	$22.82	13.483%	$25.8968	$25.90	$25.90	$25.90
7 purchase totals =	$838.51		$902.2442	$902.25	$902.30	$902.30