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	$154.53	7.802%	$166.5864	$166.59	$166.60	$166.60
Purchase #2	$29.50	10.682%	$32.6512	$32.65	$32.65	$32.70
Purchase #3	$158.64	5.612%	$167.5429	$167.54	$167.55	$167.50
Purchase #4	$201.89	13.457%	$229.0583	$229.06	$229.05	$229.10
Purchase #5	$96.46	3.677%	$100.0068	$100.01	$100.00	$100.00
Purchase #6	$222.94	6.387%	$237.1792	$237.18	$237.20	$237.20
Purchase #7	$104.68	3.473%	$108.3155	$108.32	$108.30	$108.30
7 purchase totals =	$968.64		$1,041.3403	$1,041.35	$1,041.35	$1,041.40