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	$213.70	6.661%	$227.9346	$227.93	$227.95	$227.90
Purchase #2	$63.30	11.396%	$70.5137	$70.51	$70.50	$70.50
Purchase #3	$62.29	9.839%	$68.4187	$68.42	$68.40	$68.40
Purchase #4	$118.50	7.307%	$127.1588	$127.16	$127.15	$127.20
Purchase #5	$93.31	11.369%	$103.9184	$103.92	$103.90	$103.90
Purchase #6	$166.66	3.308%	$172.1731	$172.17	$172.15	$172.20
Purchase #7	$224.99	4.511%	$235.1393	$235.14	$235.15	$235.10
7 purchase totals =	$942.75		$1,005.2566	$1,005.25	$1,005.20	$1,005.20