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	$180.72	8.588%	$196.2402	$196.24	$196.25	$196.20
Purchase #2	$64.99	12.864%	$73.3503	$73.35	$73.35	$73.40
Purchase #3	$229.64	7.390%	$246.6104	$246.61	$246.60	$246.60
Purchase #4	$230.85	11.109%	$256.4951	$256.50	$256.50	$256.50
Purchase #5	$153.90	6.816%	$164.3898	$164.39	$164.40	$164.40
Purchase #6	$167.94	10.659%	$185.8407	$185.84	$185.85	$185.80
Purchase #7	$31.66	7.399%	$34.0025	$34.00	$34.00	$34.00
7 purchase totals =	$1,059.70		$1,156.9290	$1,156.93	$1,156.95	$1,156.90