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	$148.52	5.353%	$156.4703	$156.47	$156.45	$156.50
Purchase #2	$145.31	5.168%	$152.8196	$152.82	$152.80	$152.80
Purchase #3	$101.53	11.338%	$113.0415	$113.04	$113.05	$113.00
Purchase #4	$86.47	3.495%	$89.4921	$89.49	$89.50	$89.50
Purchase #5	$224.48	5.707%	$237.2911	$237.29	$237.30	$237.30
Purchase #6	$181.49	3.531%	$187.8984	$187.90	$187.90	$187.90
Purchase #7	$127.32	9.663%	$139.6229	$139.62	$139.60	$139.60
7 purchase totals =	$1,015.12		$1,076.6359	$1,076.63	$1,076.60	$1,076.60