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	$220.47	4.610%	$230.6337	$230.63	$230.65	$230.60
Purchase #2	$39.27	13.229%	$44.465	$44.47	$44.45	$44.50
Purchase #3	$57.33	8.222%	$62.0437	$62.04	$62.05	$62.00
Purchase #4	$222.90	3.852%	$231.4861	$231.49	$231.50	$231.50
Purchase #5	$143.63	4.752%	$150.4553	$150.46	$150.45	$150.50
Purchase #6	$226.39	3.413%	$234.1167	$234.12	$234.10	$234.10
Purchase #7	$181.40	10.325%	$200.1296	$200.13	$200.15	$200.10
7 purchase totals =	$1,091.39		$1,153.3301	$1,153.34	$1,153.35	$1,153.30