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	$172.92	7.266%	$185.4844	$185.48	$185.50	$185.50
Purchase #2	$93.86	6.703%	$100.1514	$100.15	$100.15	$100.20
Purchase #3	$128.26	13.393%	$145.4379	$145.44	$145.45	$145.40
Purchase #4	$49.58	12.156%	$55.6069	$55.61	$55.60	$55.60
Purchase #5	$77.82	11.327%	$86.6347	$86.63	$86.65	$86.60
Purchase #6	$242.35	9.247%	$264.7601	$264.76	$264.75	$264.80
Purchase #7	$204.92	11.701%	$228.8977	$228.90	$228.90	$228.90
7 purchase totals =	$969.71		$1,066.9731	$1,066.97	$1,067.00	$1,067.00