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	$215.96	3.223%	$222.9204	$222.92	$222.90	$222.90
Purchase #2	$58.36	8.840%	$63.519	$63.52	$63.50	$63.50
Purchase #3	$127.41	11.117%	$141.5742	$141.57	$141.55	$141.60
Purchase #4	$163.89	5.145%	$172.3221	$172.32	$172.30	$172.30
Purchase #5	$156.50	10.337%	$172.6774	$172.68	$172.70	$172.70
Purchase #6	$120.25	9.480%	$131.6497	$131.65	$131.65	$131.60
Purchase #7	$140.52	7.196%	$150.6318	$150.63	$150.65	$150.60
7 purchase totals =	$982.89		$1,055.2946	$1,055.29	$1,055.25	$1,055.20