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	$203.37	8.309%	$220.268	$220.27	$220.25	$220.30
Purchase #2	$238.54	8.407%	$258.5941	$258.59	$258.60	$258.60
Purchase #3	$55.52	3.572%	$57.5032	$57.50	$57.50	$57.50
Purchase #4	$83.55	7.505%	$89.8204	$89.82	$89.80	$89.80
Purchase #5	$12.32	7.830%	$13.2847	$13.28	$13.30	$13.30
Purchase #6	$174.81	13.225%	$197.9286	$197.93	$197.95	$197.90
Purchase #7	$171.67	10.761%	$190.1434	$190.14	$190.15	$190.10
7 purchase totals =	$939.78		$1,027.5424	$1,027.53	$1,027.55	$1,027.50