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	$202.70	13.874%	$230.8226	$230.82	$230.80	$230.80
Purchase #2	$78.46	5.484%	$82.7627	$82.76	$82.75	$82.80
Purchase #3	$43.96	6.114%	$46.6477	$46.65	$46.65	$46.60
Purchase #4	$90.42	11.695%	$100.9946	$100.99	$101.00	$101.00
Purchase #5	$175.81	13.844%	$200.1491	$200.15	$200.15	$200.10
Purchase #6	$220.52	5.121%	$231.8128	$231.81	$231.80	$231.80
Purchase #7	$213.86	5.595%	$225.8255	$225.83	$225.85	$225.80
7 purchase totals =	$1,025.73		$1,119.0150	$1,119.01	$1,119.00	$1,118.90