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	$213.39	13.481%	$242.1571	$242.16	$242.15	$242.20
Purchase #2	$109.94	12.256%	$123.4142	$123.41	$123.40	$123.40
Purchase #3	$72.34	12.437%	$81.3369	$81.34	$81.35	$81.30
Purchase #4	$215.85	11.634%	$240.962	$240.96	$240.95	$241.00
Purchase #5	$78.97	13.189%	$89.3854	$89.39	$89.40	$89.40
Purchase #6	$129.32	4.619%	$135.2933	$135.29	$135.30	$135.30
Purchase #7	$153.97	3.534%	$159.4113	$159.41	$159.40	$159.40
7 purchase totals =	$973.78		$1,071.9602	$1,071.96	$1,071.95	$1,072.00