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	$116.62	6.483%	$124.1805	$124.18	$124.20	$124.20
Purchase #2	$181.85	3.787%	$188.7367	$188.74	$188.75	$188.70
Purchase #3	$155.94	10.655%	$172.5554	$172.56	$172.55	$172.60
Purchase #4	$204.45	11.329%	$227.6121	$227.61	$227.60	$227.60
Purchase #5	$39.57	4.697%	$41.4286	$41.43	$41.45	$41.40
Purchase #6	$164.31	12.441%	$184.7518	$184.75	$184.75	$184.80
Purchase #7	$65.77	5.314%	$69.265	$69.27	$69.25	$69.30
7 purchase totals =	$928.51		$1,008.5301	$1,008.54	$1,008.55	$1,008.60