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	$167.60	3.139%	$172.861	$172.86	$172.85	$172.90
Purchase #2	$125.90	12.355%	$141.4549	$141.45	$141.45	$141.50
Purchase #3	$129.52	11.615%	$144.5637	$144.56	$144.55	$144.60
Purchase #4	$101.84	11.179%	$113.2247	$113.22	$113.20	$113.20
Purchase #5	$147.88	12.464%	$166.3118	$166.31	$166.30	$166.30
Purchase #6	$117.58	8.448%	$127.5132	$127.51	$127.50	$127.50
Purchase #7	$77.26	12.855%	$87.1918	$87.19	$87.20	$87.20
7 purchase totals =	$867.58		$953.1211	$953.10	$953.05	$953.20