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	$84.95	5.431%	$89.5636	$89.56	$89.55	$89.60
Purchase #2	$159.46	4.191%	$166.143	$166.14	$166.15	$166.10
Purchase #3	$22.81	5.553%	$24.0766	$24.08	$24.10	$24.10
Purchase #4	$179.85	4.491%	$187.9271	$187.93	$187.95	$187.90
Purchase #5	$97.75	5.307%	$102.9376	$102.94	$102.95	$102.90
Purchase #6	$239.84	7.627%	$258.1326	$258.13	$258.15	$258.10
Purchase #7	$222.47	6.254%	$236.3833	$236.38	$236.40	$236.40
7 purchase totals =	$1,007.13		$1,065.1638	$1,065.16	$1,065.25	$1,065.10