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	$173.94	9.262%	$190.0503	$190.05	$190.05	$190.10
Purchase #2	$82.28	5.714%	$86.9815	$86.98	$87.00	$87.00
Purchase #3	$49.83	5.526%	$52.5836	$52.58	$52.60	$52.60
Purchase #4	$164.89	4.760%	$172.7388	$172.74	$172.75	$172.70
Purchase #5	$196.83	6.818%	$210.2499	$210.25	$210.25	$210.20
Purchase #6	$163.28	11.360%	$181.8286	$181.83	$181.85	$181.80
Purchase #7	$231.70	6.221%	$246.1141	$246.11	$246.10	$246.10
7 purchase totals =	$1,062.75		$1,140.5468	$1,140.54	$1,140.60	$1,140.50