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	$108.51	9.137%	$118.4246	$118.42	$118.40	$118.40
Purchase #2	$52.67	3.517%	$54.5224	$54.52	$54.50	$54.50
Purchase #3	$142.34	5.660%	$150.3964	$150.40	$150.40	$150.40
Purchase #4	$144.79	4.539%	$151.362	$151.36	$151.35	$151.40
Purchase #5	$248.97	13.577%	$282.7727	$282.77	$282.75	$282.80
Purchase #6	$160.35	13.247%	$181.5916	$181.59	$181.60	$181.60
Purchase #7	$93.35	10.171%	$102.8446	$102.84	$102.85	$102.80
7 purchase totals =	$950.98		$1,041.9143	$1,041.90	$1,041.85	$1,041.90