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	$130.34	10.871%	$144.5093	$144.51	$144.50	$144.50
Purchase #2	$149.32	4.173%	$155.5511	$155.55	$155.55	$155.60
Purchase #3	$70.79	13.192%	$80.1286	$80.13	$80.15	$80.10
Purchase #4	$153.60	7.689%	$165.4103	$165.41	$165.40	$165.40
Purchase #5	$169.96	6.387%	$180.8153	$180.82	$180.80	$180.80
Purchase #6	$133.93	8.550%	$145.381	$145.38	$145.40	$145.40
Purchase #7	$144.49	5.224%	$152.0382	$152.04	$152.05	$152.00
7 purchase totals =	$952.43		$1,023.8338	$1,023.84	$1,023.85	$1,023.80