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	$138.48	4.805%	$145.134	$145.13	$145.15	$145.10
Purchase #2	$12.67	9.582%	$13.884	$13.88	$13.90	$13.90
Purchase #3	$164.94	10.692%	$182.5754	$182.58	$182.60	$182.60
Purchase #4	$33.55	3.606%	$34.7598	$34.76	$34.75	$34.80
Purchase #5	$82.82	11.709%	$92.5174	$92.52	$92.50	$92.50
Purchase #6	$237.60	5.347%	$250.3045	$250.30	$250.30	$250.30
Purchase #7	$96.41	7.527%	$103.6668	$103.67	$103.65	$103.70
7 purchase totals =	$766.47		$822.8419	$822.84	$822.85	$822.90