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	$75.71	3.105%	$78.0608	$78.06	$78.05	$78.10
Purchase #2	$126.28	12.514%	$142.0827	$142.08	$142.10	$142.10
Purchase #3	$41.36	6.252%	$43.9458	$43.95	$43.95	$43.90
Purchase #4	$231.95	3.475%	$240.0103	$240.01	$240.00	$240.00
Purchase #5	$162.92	6.271%	$173.1367	$173.14	$173.15	$173.10
Purchase #6	$153.31	12.319%	$172.1963	$172.20	$172.20	$172.20
Purchase #7	$164.80	5.781%	$174.3271	$174.33	$174.35	$174.30
7 purchase totals =	$956.33		$1,023.7597	$1,023.77	$1,023.80	$1,023.70