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	$164.29	9.651%	$180.1456	$180.15	$180.15	$180.10
Purchase #2	$163.67	6.401%	$174.1465	$174.15	$174.15	$174.10
Purchase #3	$113.69	8.626%	$123.4969	$123.50	$123.50	$123.50
Purchase #4	$137.62	10.812%	$152.4995	$152.50	$152.50	$152.50
Purchase #5	$217.73	13.109%	$246.2722	$246.27	$246.25	$246.30
Purchase #6	$36.83	5.452%	$38.838	$38.84	$38.85	$38.80
Purchase #7	$149.33	7.624%	$160.7149	$160.71	$160.70	$160.70
7 purchase totals =	$983.16		$1,076.1136	$1,076.12	$1,076.10	$1,076.00