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	$180.84	6.438%	$192.4825	$192.48	$192.50	$192.50
Purchase #2	$225.46	5.470%	$237.7927	$237.79	$237.80	$237.80
Purchase #3	$180.42	5.328%	$190.0328	$190.03	$190.05	$190.00
Purchase #4	$91.60	12.254%	$102.8247	$102.82	$102.80	$102.80
Purchase #5	$42.71	5.669%	$45.1312	$45.13	$45.15	$45.10
Purchase #6	$145.78	4.832%	$152.8241	$152.82	$152.80	$152.80
Purchase #7	$92.68	13.196%	$104.9101	$104.91	$104.90	$104.90
7 purchase totals =	$959.49		$1,025.9981	$1,025.98	$1,026.00	$1,025.90